The secretary has made an ______ for her boss to see the doctor at 9 am. tomorrow.

A. assignment
B. opportunity
C. interview
D. appointment

________ a wrong number, we couldn't contact you over phone.

A. Having given
B. Giving
C. Having been given
D. Given

根据首字母提示，填写单词。E___________ is considered very important in business activities.

You should make a r____________ two days ahead。

All the bookings should be made in a week in a___________.

Guests must be careful to meet the d__________ in order to leave a good impression on others.

Please c________ your resersation for meeting room this afternoon.

B________ meals refer in business dealings with the business partnerr relationship for the contacts.

下列说法错误的是( )

A. 一个向量组线性无关,则该向量组的部分组也线性无关
B. 秩为1的向量组中只含有一个非零向量
C. 一个向量组线性无关,则该向量组的极大无关组唯一
D. 零向量一定可以表示成任意向量组的线性组合

设由线性方程组Ax=0 , A是4行5列的矩阵,如果R(A)=3,则其基础解系中解向量的个数为____.