Help the exhausted college student complain about their finals week by choosing the correct phrases for each gap.

"The professor explicitly told us on Monday that chapter five was excluded from the test. Because of that clear warning, we didn't need to memorize those complicated formulas, and we happily skipped them. However, I stayed up until 3 AM reading chapter six, only to discover on test day that it was an open-book exam! I needn't have lost so much sleep over it."

"Because of that clear warning, we didn't need to memorize those complicated formulas, and we happily skipped them."

The students knew in advance that the formulas weren't on the test, so they didn't study them. When you don't do something because it isn't necessary, you use didn't need to + base verb.

"However, I stayed up until 3 AM reading chapter six, only to discover on test day that it was an open-book exam! I needn't have lost so much sleep over it."

The student actually did lose sleep studying, but later realized it was a total waste of effort because the exam was open-book. When an action was done but was unnecessary, use needn't have + past participle.