The sentence that best corrects the original is: She knew the answer but didn't speak.
Explanation:
Thus, "She knew the answer but didn't speak" correctly uses the past simple tense for both actions, aligning them appropriately in time.
Identify the part of the sentence that contains a grammatical error:
Each of the boys have submitted their assignment on time.
Rearrange the following parts to form a meaningful and grammatically correct sentence:
P. a healthy diet and regular exercise
Q. are important habits
R. that help maintain good physical and mental health
S. especially in today's busy world