fifteen minutes is all i can spare为什么谓语动词是单数

you can come over now, but 10 minutes is all i can spare (ta You can come over now,but 10 minutes is all I can spare ___w All is / are good 谓语动词用?单数复数? minutes做主语,谓语动词用单数还是复数 no bird and no beast谓语动词为什么是单数? Two is enough ,为什么谓语动词用的是单数呢?而 Ten of them are teachers 却是复数 all 作主语谓语用单数还是复数,例如,all parents do is good for us.为什么用的是is My watch is fifteen minutes ( ). Fifteen minutes is a q______. fifteen minutes is a q___. can you spare me a few minutes 的"a few minutes"前面为什么不用介词“for both和all的谓语动词用单数还是复数