Question

Cathy was sitting in an armchair resting. She was tired because _____ very hard.
she's been working,she will be working,she'd been working

Answer 1

Answer:

of will fill the blank correctly.

Answer 2

Answer:

of is the right answer of this question

Explanation:

Cathy was sitting in an armchair resting. She was tired because __ of __very hard.

she's been working,she will be working,she'd been working