某机字长32位,采用定点小数表示,符号位为1位,有效值为31位,则可表示的最小负小数为( )。
A. +(231-1)
B. -(1-2-32)
C. +(1-2-31) ≈+1
D. -(1-2-31) ≈-1
Which of the following is NOT one of the four main categories of online marketing communications?
A. Web sites
B. guerrilla marketing
C. display ads
D. e-mail