Eric arrived on time, _______ it was the rush hour.

A. though    B. because    C. while    D. unless

(2017河北34题)Mom won't let Dick go out ________ he promises to be back by 10：00 tonight.

A.if B.when C.since D.unless

Bob, dinner is ready. Please wash your hands ________ you eat.

A.until B.after C.while D.before

Be more careful and more patient, ________ you will make fewer mistakes in the following experiments.

You can either e­mail us ________ come to our office for your questions.

My arm is still painful,         I'm going to see a doctor.

A.so B.for C.but D.or

Tony used to be a quiet student, ________ now he is active in class.

A.so B.and C.but D.or

Help others in need, ________ they will help you when you are in trouble.

A.and B.but C.or D.nor

You'd better be careful with the stick, ________ you will hurt yourself.

A.so B.but C.or D.and

(2017河北78题)My friends ________ I often go to the Science Club together.(盲填)