Question

I've been using this machine ___________ twelve years.
(A) Since
(B) For​

Answer 1

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☆B)For

Explanation:

In English, we use the preposition for to talk about an amount of time or space. The amount of time could be seconds, minutes, hours, days, months or even years.

The amount of time does not need to be exact. You could use for when you are talking about vague periods of time, like "for the weekend", "for ages" or "for a long time".

The important point is that for is used to specify a period of time.

In English, the basic formula for using for is this:

for + a period of time

For can be used when talking about the past, present or future.

hope it helps... :)