there is ___"u" and____ "u" in the woed umber

问题描述:

there is ___"u" and____ "u" in the woed umber

there is _a__"u" and__a__ "u" in the woed umber
应该是there is _a__"u" and_an___ "e" in the woed umber吧?为什么U 虽然是元音字母,但不是元音音素, 以元音音素开头的词 ,不定冠词才用an