Maintenance activities include(74)。

①making enhancements to software products

②developing a new software product

③correcting problems

④adapting products to new environments

A．①②

B．①③④

C．②③④

D．①②③④

[单选题] Maintenance activities include（74）.①making enhancements to software products②developing a new software product③correcting problems④adapting products to new environments（74）A．①②B．①③④C．②③④D．①②③④

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