从下面每小题的A、B、C、D四个选项中选出可以替换划线部分的最佳选项。

小题1:Shenzhen lies in the south of China.

A．keeps

B．finds

C．is

D．belongs小题2: The little girl is fortunate to get help from so many strangers.

A．Lucky

B．Excited

C．Happy

D．Grateful小题3: Liu Xiang's success came at a price.

A．Without difficulty

B．with a lot of hard work

C．With little money

D．without much time小题4: When Jason was painting the wall, some boys passed by and wanted to join him.

A．Went out

B．Went though

C．Went away

D．Went past小题5:The plane will take off in half an hour.

A．Leave for

B．Leave the ground and begin to fly

C．Remove

D．Land on the ground

测定溶液pH值时，通常使用的参比电极是（）

A.pH玻璃电极

B.饱和甘汞电极

C.氟离子选择电极

D.敏化电极