单颌多数后牙缺失，若缺隙的近远中向距离与对颌天然牙有差异，为建立良好的接触，可采用的方法为()

A．适当增加人工牙数目

B．适当减少人工牙数目

C．改变人工牙牙冠大小

D．形成尖对尖的咬合关系

E．排成对刃关系

阅读短文，根据短文内容及首字母提示，在空白处填入一个适当的单词。

Do you like animals? Do you want to keep animals? Yes, many people like animals and want to keep a lovely animal as a （71） p_____. It's a pity that they don't have a suitable place to keep them. However, keeping fish may be the best choice.

Why keep them?

People keep dogs and cats because they enjoy their friendship. Fish can not be friendly, but they have beautiful shapes and colors. It's a pleasure to watch as they swim （72）i_____ their tank（水槽）.

What do they need?

First of all, the fish need a suitable （合适的） tank, and you must fill the tank （73） w_____ suitable water. It is also good for （74） t_____ to have a few water plants in the tank to keep the water pure （纯净）. Putting a few snails （蜗牛） in the tank is a good （75） i_____. They will keep it （76） c_____

What about feeding them?

There are many kinds of fish food （77） t_____ you can get in the shops. Most are suitable for all kinds of fish. You should feed your fish only （78） o_____ a day. It is important not to give them （79） t_____ much food. Just give them as much as they can （80） e_____ up in about 15 minutes. This will keep them healthy.