It's _____(a,an) useful and ____(a,an) unusual record.

It's _____(a,an) useful and ____(a,an) unusual record. 为什么unusual前用a而useful前用an it's（ ）useful book a.quite b.a quite c.quite an d.an quite 是a unusual还是an unusual most an unusual 还是 a most unusual ( )useful book a/an It's an unusual thing for us to find ______ UFO.A.a B.不填 C.a This is _____ book. And it is ____ English book. A．a, a B．an He has _____ useful book.(填an或a) There is a(an) useful book and some pens in it an useful animal?还是a useful animal? What colour is ______ orange?－It’s _____ orange.A.an,an B.an