There is a(an) useful book and some pens in it如题 用 a 还是 an

There is a(an) useful book and some pens in it如题 用 a 还是 an
There is a(an) useful book and some pens in it
如题 用 a 还是 an

There is a(an) useful book and some pens in it如题 用 a 还是 an
用a
useful 的读音开头不是元音

a，确认是这个