Question

My mother was tired yesterday because she __(not sleep) well night before

Answer 1

My mother was tired yesterday because she couldn't sleep well the night before.

Why did we use past tense in the second clause?

• If the first clause consists of past indefinite tense, the second part must consist of past indefinite or past perfect.
• If the first clause consists of present indefinite, the second clause should be in present indefinite or future indefinite.
• The above sentence can also be written as: My mother was tired yesterday because she did not sleep well the night before.