1.The political future of the president is now hanging by a __.
A thread B cord C string D rope
2.The question is still__ discussion.
A in B by C for D under
3.We managed to reach the top of the mountain, and half an hour later we began to __.
A ascend B descend C decline D plunge
4.To survive in the intense trade competition between countries, we must__ the qualities and varieties of products we make to the world-market demand.
A improve B enhance C guarantee D gear
5.There has been a __ lack of communication between the union and the management.
A regretful B regrettableC regretting D regretted
（做完后才能看答案哦！）