将会计凭证划分为原始凭证和记账凭证的依据是会计凭证( )。

A．编制的时间

B．取得的来源

C．填制的程序和用途

D．反映的经济业务内容

Maintenance activities do not include ______.

A．making enhancements to software products
B．developing a new software product
C．correcting problems
D．adapting products to new environments