我国使用哪些计量检定印证？

为建设和谐新农村，某镇决定修一条便民路，已知这项工程由甲队单独做需40天完成；如果由乙队单独做10天，剩下的工程还需两队合做20天才能完成。

(1)求乙队单独完成这项工程需多少天？

(2)两队合做这项工程需多少天？

将熔化金属喷射到被镀物件表面所用的雾化气是（）。

A．氮气

B．氩气

C．氧气

D．压缩空气

二次回路的编号根据等电位的原则进行。

Dudu is a keen birdwatcher whose house is near a dam on which some rare birds have taken up residence. Unfortunately her neighbour’s wall and large tree prevented her from getting a good view of the dam.She entered into a contract with Jabulani to build a special 12-metre high observation tower that would enable her to see the dam. It had to be at least 12 metres high to give her an unobstructed view of the dam. Unknown to Jabulani, Dudu also entered into an agreement with Diskom (Pty) Ltd to permit them to use the tower to transmit their cellular phone signals. The agreement provided that Dudu would be paid P20,000·00 on installation, and an annual rent of P10,000·00 per year.When the tower was finished it was only 10 metres high and, although Dudu could see over the wall, the tree still partially obscured her view. Also, the height of the tower was too low for Diskom (Pty) Ltd to make use of it.As it stands the tower cost P30,000·00. Had Jabulani built it to the specified height it would only have cost a further P2,000·00. However, because of the special construction its height cannot now be increased.Required:Analyse the rights that Dudu has in contract law against Jabulani.In particular advise her with regard to:

(a) whether she can get an order for specific performance to require Jabulani to rebuild the tower; and (5 marks)

我国海河平原最大的湖泊是( )。

A．大明湖
B．微山湖
C．洪泽湖
D．白洋淀