10.某小组5名同学在一周内参加体育锻炼的时间如下表所示,关于“锻炼时间”的这组数据,以下说法正确的是( )
| 锻炼时间(小时) | 2 | 3 | 4 | 5 |
| 人数(人) | 1 | 1 | 2 | 1 |
| A. | 中位数是4,平均数是3.5 | B. | 众数是4,平均数是3.5 | ||
| C. | 中位数是4,众数是4 | D. | 众数是5,平均数是3.6 |
8.下列各值中是方程组$\left\{\begin{array}{l}a+b=3\\ a-b=1\end{array}$的解的是( )
| A. | $\left\{\begin{array}{l}a=1\\ b=2\end{array}$ | B. | $\left\{\begin{array}{l}a=2\\ b=1\end{array}$ | C. | $\left\{\begin{array}{l}a=3\\ b=1\end{array}$ | D. | $\left\{\begin{array}{l}a=4\\ b=5\end{array}$ |
7.下列不属于二元一次方程组的是( )
0 283448 283456 283462 283466 283472 283474 283478 283484 283486 283492 283498 283502 283504 283508 283514 283516 283522 283526 283528 283532 283534 283538 283540 283542 283543 283544 283546 283547 283548 283550 283552 283556 283558 283562 283564 283568 283574 283576 283582 283586 283588 283592 283598 283604 283606 283612 283616 283618 283624 283628 283634 283642 366461
| A. | $\left\{\begin{array}{l}x+y=3\\ x-y=1\end{array}$ | B. | $\left\{\begin{array}{l}x=3\\ x-y=1\end{array}$ | C. | $\left\{\begin{array}{l}x+y=3\\ y=1\end{array}$ | D. | $\left\{\begin{array}{l}xy=3\\ x-y=1\end{array}$ |