The scientist _______ the new theory last year is now conducting further research on it.

• a) who proposed

The correct answer is "who proposed" because "who" is used for referring to people (the scientist), and "proposed" is the verb in the past tense.

Sử dụng cấu trúc bị động để viết lại câu sau:

• "The company will announce the new product tomorrow."
• The new product will be announced by the company tomorrow.

This is the passive form, where "will be announced" is used instead of the active "will announce."

Hoàn thành câu với dạng đúng của động từ trong ngoặc:

• If I were you, I would consider his offer more carefully.

In the second conditional (used for hypothetical situations), "were" is used after "I" (though "was" is sometimes used in informal speech). The second verb "consider" is in the base form.