【单选题】Which of the following creates an incentive to increase the amount of an activity?
A.
an increase in the marginal cost of the activity and a decrease in the marginal benefit of the activity
B.
a decrease in the marginal cost of the activity and an increase in the marginal benefit of the activity
C.
constant marginal cost and constant marginal benefit of the activity
D.
None of the above create an incentive to increase the amount of an activity.
【简答题】若A1和A2两表以共同的“学号”字段建立联接查询,有8条学号相同的记录,各自有2条不相同的记录。左联接有____条记录。
【简答题】产品设计中的 “ 三化 ” 主要是指 、 、 。 1、 机器由 、 和 组成。
【简答题】继电器主要由 机构、 1 机构和 机构三部分组成。
【判断题】Language testing is a complex activity which is guided by linguistic and psychological theories. ()
【单选题】The activity was delayed,______ was exactly______ we wanted.
【单选题】如果需求的收入弹性为-0.80,由于收入变化,需求量增加了10%,则收入( )
【简答题】若A1和A2两表以共同的“学号”字段建立联接查询,有8条学号相同的记录,各自有2条不相同的记录。完全联接有____条记录。