问题
单项选择题
主要存在于细胞内。对细胞内渗透压的维持起重要作用的是______。
A．钙
B．镁
C．钠
D．钾
E．锌
答案
参考答案：D
搜题请搜索小程序“爱下问搜题”
主要存在于细胞内。对细胞内渗透压的维持起重要作用的是______。
A．钙
B．镁
C．钠
D．钾
E．锌
参考答案：D
完形填空（共20小题；每小题1分，满分20分） While attending a conference, I returned to my hotel room late one rainy evening．The overhead light outside my door was 1 and I had difficulty finding the keyhole．When I finally 2 to open the door, I 3 around the wall for a light switch．I found a 4 where a switch was once installed．．．but no switch． No discouraged easily, I remembered seeing a 5 by the bed when I put away my luggage 6 in the day．I found the bed in the dark and felt around until I found the lamp, but when I switched it on, 7 happened! Now what? Though I knew that it was dark outside my window 8 the outdoor light was burned out, I thought that 9 if I opened the curtains I might be able to use the light from the 10 to find another lamp．So I 11 my way slowly across the room to the curtains and．．．no draw-string! I finally stumbled （跌跌撞撞） around until I found a desk lamp that actually 12 ! That evening I discovered in a whole new way just how dark the world can be and how necessary 13 is． But even more necessary than 14 light is the light that shines from people—the light of love, sympathy and 15 ．Because, for many people, the world is a dark and 16 place． It is the shining that is important, for someone today just may be stumbling in discouragement or fear and in 17 of some light． So let your light shine．Whatever light you 18 may be a beacon （灯塔） of hope and encouragement in someone’s darkness．And if you feel that your light is 19 a candle in a forest, remember this—there isn’t enough darkness in the world to 20 the light of one small candle．
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