用所给单词的适当形式填空。

     The Winter Olympics are also called the White Olympics. Always, many colourful stamps 1.____

______(publish) to mark(纪念) the great Games. The first stamps marking the opening 2.__________

(come) out on January 25, 1932 in the United States for the 3rd White Olympics. From then on, 3.______________(publish) stamps during the Winter Olympics became a rule. During the 4th Winter Olympic

Games, some special stamps 4.__________(publish) in Germany in  November of 1935. The five rings

of Olympics 5.__________ (print) on the front of the sportswear. It was the first time that the symbol

6.__________(appear) on the stamps of the Winter Olympics.

将20克的20%氢氧化钠溶液与10克20%的稀硫酸混合，混合后溶液是（　　）

A．pH＞7

B．pH=7

C．pH＜7

D．滴入紫色石蕊试剂不变色