An action in a sentence can be represented in two ways, namely active and passive voice.

The passive voice always uses the past participle form of the main verb irrespective of any tense. Only the auxiliary verbs depend upon the sentence given in the active voice.

The correct answer is A)Considerable efforts are being made by tobacco manufacturers to gain new clients.

The option A is correct as the given sentence is in active voice and to transform it into passive voice the subject of the given sentence 
(Tobacco manufacturers) comes in the place of the object(considerable efforts) and vice versa. Also, as the sentence is in the present continuous tense, 'being' is added after the helping verb 'are' and before the past participle form of the main verb(make).

Options B, C, and D are wrong as the sentence is not in the past continuous tense, 'are made' cannot be used, and the sentence structure is wrong respectively. respectively.