Which of the following is not one of the occasions for writing a thank-you letter（）
A. for hospitality
B. for presents or contribution
C. for congratulation
D. for apology
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You may borrow the book ______ you keep it clean（）
A. as long as
B. when
C. after
D. unless
把RNA转移到硝酸纤维素膜上的技术叫（）
A. Southern blotting
B. Northern blotting
C. Western blotting
D. Eastern blotting
Which of the following biasing combinations is not normally associated with one of the three transistor operating regions（）
A. E-B junction = forward, C-B junction = reverse
B. E-B junction = reverse, C-B junction = reverse
C. E-B junction = reverse, C-B junction = forward
D. All of the above
VCE is measured ______（）
A. from the emitter terminal to ground
B. from the collector terminal to the emitter terminal
C. from the collector-emitter junction to ground
D. None of the above
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