抢险救援靴帮耐弯折性能经反复弯折()次后,无裂纹、松面、掉浆等现象。
A.20000.0
B.10000.0
C.15000.0
D.5000.0
参考答案:A
Students ___________ remain in their seats until all the papers have been collected.
A.may
B.shall
C.need
D.can
影响节流温降效果的因素有哪些?