There is an s and a u in this word.为什么对呢

s发音为[es],以原音音素开头
u发音为 [ju:],以辅音音素开头
所以这里是an s和a u
关键是要弄明白不是看元音字母还是辅音字母开头,而是看是原音音素还是辅音音素,原音音素前加an,辅音音素前加a