The correct symbol of "therefore" is __________.[ ]
A. ∵
B. ∴
C. <
D. >
答案:B
下列各计算结果是正数的有( )个.
①-(-2);②-|-2|;③-(-3)2;④[-(-3)]2
A.1
B.2
C.3
D.4
停工待检点指的是:()
A.H
B.R
C.W
D.S