490. frustrate vt. 使沮丧

Although unknowns and uncertainties frustrate people, they in turn color our life. 不可预测令人倍感挫折与沮丧，却也因此而使人生精彩。

491. guarantee vt. /n. 保证

There is no guarantee for blacks to exercise their rights.（2006年6月17日大学英语四级(CET-4)真题试卷(A卷)）

492. guilty a. 内疚的；有罪的

All this proved him to be the guilty man.

这一切都证明，他就是那个有罪的人。

493. jealous a. 妒忌的

Once upon a time in a great castle, a Prince's daughter grew up happy and contented, in spite of a jealous stepmother.

很久很久以前，王子的女儿虽然有个忌妒心很强的继母，她依旧在宏伟的城堡中快乐满足地成长。

494. jeans n. 牛仔裤

I like the cut of those jeans .

我喜欢这件牛仔裤的剪裁。

495. liquor n. 酒，烈性酒

Virtually all restaurants have liquor licences.

几乎所有餐馆都有售酒执照。

496. liter/litre n. 升

Nearly all the volunteers drank black tea regularly consuming on average more than a liter each day.

几乎所有的志愿人员定期喝红茶，每天平均超过一公升。

497. modest a. 谦虚道

The learned are the most modest.

有学问的人是很谦虚的。

498. molecule n. 分子

Almost any kind of molecule might be evolved.

几乎任何一种分子都能被演化。

499. orbit n. 轨道 v. （绕...）作轨道运行

We are orbiting the moon.

我们正在环绕月球运行。

Venus circles the sun in an almost perfectly round orbit.

金星几乎以正圆形的轨道围绕太阳运行。

500. participate v. (in) 参与，参加

Everyone can participate in this game.

每个人都能参加这游戏。

501. particle n. 微粒

Particle system is an effective method in rain simulation.

粒子系统是模拟雨的一种有效方法。

502. particularly ad. 特别，尤其

He recommends that we don’t stay silent over inappropriate behaviour, particularly with regular visitors.（2008年12月大学英语四级考试真题）

503. respond vi. 回答，答复；反应

LeDoux studies the way animals and humans respond to threats to understand how we form memories of significant events in our lives. （2006年12月24日大学英语四级(CET-4)真题试卷(A卷)）