变压器铭牌上标注有额定电压％，是说明该变压器是（）。

A、有载调压

B、三级调压

C、无载调压

D、三级有载调压

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