8086CPU中段寄存器用来存放（） A.存储器的物理地址 B.存储器的逻辑地址 C

Go on with your English study. _____ is difficult if you put your heart into it.　　[ ]

A. Anything

B. Something

C. Nothing

上呼吸道感染是百病之源。

已知由激光器发出的一细束功率为P=0.15 kW的激光束，竖直向上照射在一个固态铝球的下部，使其恰好能在空中悬浮。已知铝的密度为ρ=2.7×10³kg/m³，设激光束的光子全部被铝球吸收，求铝球的直径是多大？(计算时可取π=3，g=10 m/s²)

水泵不得在如下情况下运行（）。

A、泵内无水情况下

B、汽蚀情况下

C、无人看守

D、闸阀闭死情况下长期运行

Rapid application development (RAD) systems purport to lighten the developer’s (46) by making it easy to program an application with simple intuitive steps.
RAD tools (47) the developer everything needed to construct a fully functional application quickly and easily. They make short work of modifying the developed product to (48) changes after the program is finished. Applications developed with RAD tools are constructed as they are envisioned. As an application’s real usefulness (49) , the developer armed with RAD tools should be able to (50) on new features with little fuss.

A．appearances

B．emerges

C．recognizes

D．solves