应力不变量说明（）。

A.应力随着截面方位改变，但是应力状态不变

B.一点的应力分量不变

C.主应力的方向不变

D.应力状态特征方程的根是不确定的

The heat generated by the operating system war between rivals IBM Corp. and Microsoft Corp. is (21) .
Windows 95 and OS/2 introduce a new (22) . Both systems claim to multitask legacy DOS and 16-bit Windows applications. However, only OS/2 can provide full memory (crash) protection for these legacy applications because it is capable of running each DOS and Windows application within its full-protected memory address space.
Windows 95 will run all current Windows applications in the same shared- memory address space, affording full memory protection only to the (23) 32-bit Windows 95 applications. In other word, Windows 95 users will have to (24) their current Windows applications to Windows 95 version to match the memory protection OS/2 now delivers.
While OS/2 does afford superior memory protection and multitasking for legacy DOS and Windows applications, it will not be able to run any Windows 95 applications. IBM may address this (25) in an update of the OS but has no present plans to do so.

A．old

B．big

C．new

D．original