In the given question you will find sentence, part of which are `"bold"`. compare the `"bold"` part of each sentence with the expressions (a),(b) and (c) given below. choose the expression which is an improvement upon the `"bold"` part. If none of the three expressions improves the sentence,then your answer is (d).
I am tired as `"I am working"` since 7 O'clock in the morning.

Options

A. I was working
B. I had been working
C. I have been working
D. no improvement

Answer

C