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【简答题】
紫色牵牛花瓣的浸取液在不同的酸碱性溶液中会呈现不同的颜色（见下表）．因此，可作代用酸碱指示剂． 物 质 食用白醋 石灰水 食盐水 紫色牵牛花瓣浸取液颜色 红色 蓝色 紫色 某课外活动小组用自制的上述指示剂来测定某雨水样品的酸碱性，发现指示剂呈红色．则该雨水呈______性（选填“酸”或“碱”或“中”），雨水中pH______7（选填“大于”或“等于”或“小于”）．造成雨水这一结果的原因是______．
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反馈参考答案：
举一反三
【单选题】What shall we do if we suspect the identity of a journalist?
A.
Ask him/ her to hold on and call to the reception desk to check the identity.
B.
Ask him/ her to wait a minute and check his/ her passport and visa
C.
Ask him/ her to wait a minute and consult “Who is who”.
D.
Ask him/ her to wait a minute and call to the information center to check the identity.
【单选题】We shall call on her as soon _____.
A.
as she will come
B.
as she came
C.
as she comes
D.
she comes
【单选题】We shall call on her as soon ___________.
A.
as she will come
B.
as she shall come
C.
as she comes
D.
she comes
【单选题】— When shall we go to visit her? — Take your time. I'll ____ you at your office then. [ ]
A.
call
B.
call on
C.
call at
D.
call for
【单选题】We shall call on her as soon ______.
A.
as she comes
B.
she comes
C.
as she shall come
D.
as she will come
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