在HTML中，单元格的标记是（）。
A.<td>
B.<span>
C.<tr>
D.<body>
参考答案：A
离心式压缩机（）无法用理论计算出来。
The chairman asked many questions ________ the education of the homeless children in that area.
A．concerned
B．concerning
C．to concern
D．having concerned
of the homeless children in that area.