The correct answers are travels and is traveling.
Explanation:
In clauses of time referring to the future (introduced by words like while, when, as soon as, before, after), we cannot use future tenses like "will travel" or "will be traveling."
Instead, we use present tenses:
- The Present Simple (travels) states the future fact within the time clause.
- The Present Continuous (is traveling) is also perfectly correct and emphasizes the ongoing, continuous nature of the action while the reading happens.
"Travel" is incorrect because it lacks the necessary third-person singular "s" for "the train."
Present tense
If you've ever told someone I am living here for ten years (should be have lived or have been living) — you've hit the present perfect's main puzzle. English insists that "started in the past, still true now" lives in the present perfect, not the simple present. Internalise that one rule and a whole class of common errors disappears.
The present tense in English has four forms: simple present (I work) for habits and general truths; present progressive (I am working) for now or temporary; present perfect (I have worked) for past with present relevance; present perfect progressive (I have been working) for ongoing duration up to now.
Future tense
If you've ever wondered why a native speaker said I'm meeting her tomorrow instead of I will meet her tomorrow — you've felt the future-tense puzzle. English has at least four common ways to talk about the future, and they're not interchangeable. Pick the wrong one and you sound either unnaturally formal or surprisingly vague about your own plans.
English uses several constructions for future time: will + infinitive (predictions, spontaneous decisions: I'll call), be going to (planned intentions, evidence-based predictions: It's going to rain), the present continuous for arrangements (I'm meeting Sam at six), and the present simple for fixed schedules (The train leaves at 8).
Clause
If you've ever been told your sentence is a "run-on" or that you've used a comma where there should be a semicolon — you've hit the limits of writing without seeing clauses. Get this concept solid and most punctuation problems quietly disappear: you can finally tell a complete thought from a fragment without guessing.
A clause is a grammatical unit built around a verb, usually with a subject and a predicate. Independent clauses stand alone (I missed the bus); dependent clauses can't (Because I overslept). Combine them and you build complex sentences.
Simple tense
If you're at A1/A2 and the array of English tenses feels overwhelming, here's the good news: most of what you need to say at the start fits in the simple forms. I work, I worked, I will work — three forms cover habits, completed past actions, and basic future. Master these first; the progressive and perfect come more easily once the simple is solid.
The simple aspect is the unmarked verb form — no progressive -ing, no have + past participle. I go, I went, I will go. Marks single completed actions, habits, or permanent states.
Progressive tense
If you've ever paused over I work in London vs I'm working in London and not been sure which to pick — you've hit the simple/progressive distinction. The first means it's your usual job; the second means it's temporary, going on right now. Native speakers reach for this distinction constantly without thinking; learners have to make it deliberate.
The progressive aspect marks ongoing action at a time of reference, formed with be + -ing: I am working, She was reading, They will be travelling. Marks temporary or in-progress events. Stative verbs (know, believe, own) don't normally take it.
B2 | Upper Intermediate
If a university admissions team or visa office has ever asked you for an English test score, B2 is probably the level they had in mind. It's the threshold where your English stops being a constraint and starts being a tool — and the line between B1 and B2 is often the line between "stuck in beginner classes" and "ready to study or work in English."
B2 is the upper-intermediate level in the CEFR framework, demanding flexible control of mixed conditionals, passive voice across tenses, reported speech with backshifting, and participle clauses.
Difficulty: Hard
If easy and medium questions are clicking but you still feel exposed in real conversation or formal writing, you've outgrown the basics. Hard material is where the gaps you didn't know you had show up: the distractor that "sounds right", the rule that interacts with another rule, the case where context changes the answer. It's where genuine fluency is built.
The Hard difficulty tag marks upper-intermediate to advanced challenges — typically B2 and above. Interacting rules, edge cases, plausible distractors, and contexts that require genuine understanding rather than surface pattern-matching.