There is ____ “o” and ____ "f" in the word "of"

There is ____ ''b'',____ ''u'' and ____ ''S'' in the word '' There is ____“u” and ____“r”in the word “your” There is ___"o" and ____"u"in the word "house" A.a,a B.an,an there is ____（a/an）“o” in this word. There is ____ s and ___u in the word 填a还是an? There is ____"u" and ____ "s" in the word "bus''这一类题目怎么分辨用a还 There is ____ “ m ” in the word “mother”. 1.There is ____ "h" in the word "hour" There is ____"U" in the word bus . There is ____ "o" and ___ "l" in the world "bowl" There is ()“f”,()“u”and () “n” in the word“fun” There is ()"f" and ()"d" in the word "friend"