Question

Fill in the blank with the most appropriate word.
This nuclear power station let __________ a cloud of dangerous gases.

• A. down
• B. in
• C. off
• D. out

Answer 1

Answer: (C)

off

Option C is the correct answer because the preposition 'off' is used with the verb 'let' to form the phrasal verb 'let off' which means to release (liquid, air, etc) .

Note that the prepositions provided in the options are added to the verb 'let' so as to form different phrasal verbs. Phrasal verbs are basically multi-word verbs.

Option A is incorrect because 'let down' means to disappoint and this usage is incorrect in the given sentence.

Option B is incorrect because 'let in' means to allow to enter.

Option D is incorrect because 'let out' means to allow to leave a place.