has doing是什么时态

　　Each nation has its own peculiarities when it comes to doing business.

　　说到做生意，每个民族都有它自己独有的一些特性。

　　The government has been doing some blue-sky thinking on how to improve school standards.

　　就如何提高学校的水平，政府仍然在作一些漫无边际的构想。

　　Embarrassment has kept me from doing all sorts of things.

　　难为情使得我什么也做不了。