Experiments of this kind ___in both the U．S and Europe well before the Second World War
#100340
A
had conducted
B
have conducted
C
have been conducted
D
had been conducted
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After months of voyage, Columbus arrived in what later to be a new continent.
#101234
A
had been proved
B
was proved
C
had proved
D
proved
—Bob! How’s your project? I heard you started it last Friday, right?—Oh! I ______ for it. But I haven’t decided when to do it.
#100718
A
had prepared
B
was preparing
C
have been preparing
D
have prepared
—— Can’t you notice the person shaking hands with the leader? He is our classmate Tom! —— Oh, my God ! I ____________ him.
#101035
A
don’t recognize
B
didn’t know
C
don’t know
D
didn’t recognize