【C19】A．whenB．whereC．howD．if

【C5】A．whenB．whichC．howD．it

【C7】A．whenB．whereC．howD．what

【C17】A．whenB．thatC．howD．what

【C6】A．whenB．whereC．whichD．that

【C9】A．whenB．whereC．whyD．how

【C17】A．whenB．whereC．whyD．how