第1个回答 2012-04-20
When + Perfect词 + will 相等于 “当。。。了的时候“
When finished, this building will be 300 meters tall.
When taken, this medicine will help you to sleep at night.
When broken, the alarm will go off.
When done, the system will send the email to the client.
When dropped, the hard disk will lock-up to protect the data.
Is being + 过去词 指现在正在进行，而且快要完工了。
The house is being completed now.
The data is being prepared now.
The cake is being readied now.
Was being + 过去词 指现在过去正在进行，而且当时快要完工了。（而现在完成了）
In 1946, this house was being completed.
2 days ago, the data was being prepared by the computer.
Last night the cake was being prepared.
第2个回答 2012-04-20
A
when引导条件状语从句，从句用一般现在时，主句用一般将来时。
此句相当于省略了the museum is （completed），当从句和主语主语一致时，是可以这样省略的。
A选项是一般现在时的被动形式。B选项是现在进行时的被动，不对。
不懂追问。
追问什么情况下用 being done句型？
追答表示正在进行啊。
此句意为：当博物馆修好后，它将对公众开放。
给个being done的例子：The museum which is being built will be open to the public next year.正在修建的博物馆明年开放。