Because the shop ________ , all the T-shirts are sold at half price.

A．has closed down

B．closed down

C．is closing down

D．had closed down

验电器的检查内容及规范：绝缘杆无（）、脏污、受潮等情况，验电器发光及声响完好，电池电量充足，报警声无时断时续的情况。

A、放电

B、龟裂

C、破损

D、断裂