您要查找的是不是：
- N选X系统XooN
- 备选optional
- 报警系统panalarm
- 备选方案alternative (Alt.)
- 运输系统belt line
- V+X+N（L）V+X+N(L)
- 选股select stocks
- 安全系统security system
- 我们用x表示一个未知数。We use x as the symbol for an unknown quantity.
- 帮助系统help system
- 再选reelection
- 照明系统illuminating system
- 备选者choice
- y 2 和x n 中，2和n为上标。In y2 and xn,2 and n are superscripts.
- 保障系统safeguards system
- 他们被选去探路。They were chosen to scout the trail.
- 他们在设计道路系统。They are devising a road system.
- 精挑细选choose
- 折射率n(x)在波导截面内是逐渐变化的。The refractive index n(X) varies gradually over the cross-section of the guide.
- 电路与系统Circuits and Systems
