普通型消防救生气垫充气时间是()s,补气时间是()s。
A.≤50,≤30
B.≤60,≤30
C.≤60,≤20
D.≤50,≤20
参考答案:B
This book is said to be a special one,which________many events that cannot be found in other history books.
A.writes
B.covers
C.prints
D.reads
阿魏在贮藏中容易发生()
A.变色
B.潮解
C.粘连
D.泛油
E.霉变