Someone must have left the tap on, ______ the water was running over and flooding the bathroom.
A. for
B. moreover
C. nevertheless
D. therefore
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Human behavior is mostly a product of learning, ______ the behavior of animal depends mainly on instinct.
A. whereas
B. so
C. unless
D. that
the Europeans knew what compass was, the Chinese had put it into practical use.
A. Before long
B. Long since
C. Long ago
D. Long before
She thought I was talking about her daughter, ______ in fact I was talking about my daughter.
A. because
B. unless
C. while
D. therefore
He hasn’t yet arrived. He may, ______, come later.
A. but
B. if
C. or
D. however