In question below fill the gap with the appropriate option:
Four engineers _____ on this system since March
Answer Details
The most appropriate option to fill the blank is "have been working."
Explanation: The use of "since March" indicates that the action started in the past and is still ongoing. "Have been working" is the present perfect continuous tense and is used to describe actions that started in the past and continue up to the present. So, the sentence means that the four engineers started working on the system in March, and they are still working on it.