Retired Moderator
Joined: 07 Jun 2014
Posts: 4815
Given Kudos: 0
WE:Business Development (Energy and Utilities)
Re: While most of the tasks undertaken by the interns were
[#permalink]
13 Sep 2017, 17:39
Explanation
The trigger while indicates that most of the tasks, which are described as undemanding, differ from the one described in the blank; hence, you need a word like demanding. Both arduous and onerous can mean demanding, so choices (C) and (D) give you appropriate, equivalent sentences. Choices (A) and (F) give you synonymous meanings, but nothing in the sentence supports the description of the tasks as clear.
Hence options C and D are correct!