多项选择题 小组工作相对于个案工作有以下优势：（）。

单项选择题 Mr. Brown Smith555 King Street Auckland New ZealandDear Mr. Smith, I'm writing to complain that you didn't install the central heating system in my house. We should have the heating on Oct. 10th. When we discussed the matter on installation, you promised that it would he made before Oct 10th. However, it is 7 days past the deadline, and no engineers come to install it. It makes a lot of trouble for our family. We appreciate your seeing the matter seriously and arranging for the installation within 5 days. I'm sorry to say if you are still unable to install them by Oct 80th, we shall reluctantly cancel our order and ask for compensation. Sincerely yours, Nancy WebsterWhy does Nancy write to Mr. Smith?A．Because Nancy should correct a mistake in her contract with Mr. Smith.B．Because Nancy wants to complaint about none installation to Mr. Smith.C．Because Nancy wants to establish a further business relationship with Mr. Smith.D．Because Nancy plans to install the heating system in other days.

多项选择题 社区社会工作需要注意：（）。