He wrote a letter ________ he explained what had happened in the accident.
| A．what | B．which |
| C．where | D．how |
He invited me to a dance after the show ________ Christmas Eve.
| A．at | B．on | C．in | D．by |
Would you mind not picking the flowers in the garden？They are ________ everyone's enjoyment.
| A．in | B．at | C．for | D．to |
My father warned me ________ going to the West Coast because it was crowded with tourists.
| A．by | B．on | C．for | D．against |
Nowadays some hospitals refer to patients ________ name，not case number.
| A．of | B．as | C．by | D．with |
With ________ successful launching of Tiangong1，China's space dream has taken ________ step closer to reality.
| A．the；a | B．/；a | C．a；the | D．the；/ |