Explanation:

Correct Answer is (a).We use the present perfect continuous tense to talk about an action that started in the past and is continuing now. This is often used with 'for' (showing period of time) or since (showing point of time).
As the given sentence is one, the prepositional phrase 'from the last' must be replaced with 'for past' to make it a grammatically correct sentence. Hence, the option A is correct.