Is or are? Why?

ambidextrous At the end of the conference two hours is/are spent on reviewing and summarizing.

At the end of the conference, two hours are spent on reviewing and summarizing.

Hours is plural form, are.

ambidextrous At the end of the conference two hours is/are spent on reviewing and summarizing.

Is. "Plural unit words of distance, money, and time. take a singular verb."

I wouldn't use "on" there. We spend time doing things, we don't spend time on doing them. Some of u

but isn't this two hours considered as a unit??
I mean if you google this: "two hours is spent on" with the quotations you'll see a lot of examples of what I mean.

how about this one:
the first five years were/was* difficult *ones/one.

ambidextroushow about this one:the first five years were/was* difficult *ones/one.

Good one. The first five years was a difficult time because they were difficult ones. English takes delight in trashing every rule you throw at it. You always have to use common sense.

It just comes down to whether you are thinking of things as a block or as separate pieces.

These two dollars are all I have. -- I'm thinking of each dollar separately.
Two dollars is a great price for breakfast. -- I'm thinking of the sum.

With the original sentence, it could go either way. "Gee, we only have 16 hours at this entire conference, and they want to spend two of t