Question

sat #1 reading & writing - part 1 21 of 27 next 01:05:43 in 2019, the international definition of a kilogram was changed to refer to plancks constant, an unchanging value foundational to quantum physics. previously, a kilogram ________ defined as the mass of one particular object: a cylinder of platinum - iridium alloy called the international prototype of the kilogram (ipk). which choice completes the text so that it conforms to the conventions of standard english? a had b were c had been d have been

Explanation:

The action of defining the kilogram as the mass of the IPK happened before 2019. The past - perfect tense "had been" is used to show an action that was completed before another past action (the change in 2019). "Was" is not correct as it doesn't convey the prior - to - another - past - action sense. "Were" is plural and "a kilogram" is singular. "Have been" is present perfect and not appropriate for a past - before - another - past situation.

Answer:

C. had been