题目内容
The Bunsen Burner is so named because it is thought _________ by Robert Bunsen.
[ ]
A.
to be invented
B.
having been invented
C.
invented
D.
to have been invented
答案:D
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题目内容
The Bunsen Burner is so named because it is thought _________ by Robert Bunsen.
to be invented
having been invented
invented
to have been invented