The Mathematics teacher made us commit the formula … memory.

Analyze the question: This tests your knowledge of prepositions that go with a fixed expression (idiom). The expression is "commit something ___ memory."

Explain the concept: In English, the idiom is "commit to memory", which means to memorize something so well that you can recall it without looking. It is a fixed phrase, so the preposition cannot be swapped for another.

Don't confuse it with similar phrases:

• commit to memory = memorize
• commit to paper/writing = write down
• commit to someone's care = entrust

Step-by-step solution:

1. The verb is "commit," and the object is "the formula."
2. We need a preposition to link the verb and object to "memory."
3. Test each option: • A. "commit the formula on memory": wrong, not an English idiom • B. "commit the formula to memory": correct, a standard idiom • C. "commit the formula into memory": incorrect usage, since "into" is not used in this idiom • D. "commit the formula by memory": wrong; "by memory" is not used here (compare "learn by heart")

Complete sentence: The Mathematics teacher made us commit the formula to memory.

Answer: B. to

Exam tip: Learn idioms as whole chunks, not as separate words. Pair them up like this: commit to memory, learn by heart. If a phrase sounds like something you've heard in a textbook or from your teacher, it is probably the correct fixed expression.