In this sentence

①a contentious issue / topic / matteradj.有争议的；引起分歧的

Synonymscontroversial, disputed, debatable

句中 contentious 用来修饰 trade issues（贸易问题），指中美两国在出口管制等议题上存在巨大分歧、极易引发激烈争执，因此是“引起争论的、有争议的”这一核心用法。

• Freedom of speech is of no use whatsoever if people must avoid contentious issues.如果人们必须回避有争议的问题，言论自由就毫无用处。— John Mortimer

②sb is contentiousadj.好争吵的；爱抬杠的

Synonymsquarrelsome, argumentative, pugnacious

• It is better to dwell in the wilderness, than with a contentious and an angry woman.宁可住在旷野，也不与好争吵、易发怒的妇人同住。— Proverbs 21:19

In this sentence

①frustratingly + adj. / adv.adv.令人沮丧地；令人懊恼地（修饰形容词或副词，表示程度令人不快）

Synonymsannoyingly, irritatingly, exasperatingly

原句中出现的是名词形式 frustration（沮丧、懊恼），副词 frustratingly 常用于修饰形容词或副词（如 frustratingly slow、frustratingly brief），表示某事物的状态或程度令人感到失望、无奈。

• Wisdom often arrives frustratingly slow, while foolishness moves with effortless speed.智慧的到来往往缓慢得令人心焦，而愚昧的蔓延却总是轻捷迅疾。

②frustratingly, [sentence]adv.令人遗憾的是；令人无奈的是（作评注性状语修饰全句）

Synonymsregrettably, vexingly

• Frustratingly, we often recognize life's greatest lessons only after the moment to apply them has passed.令人无奈的是，我们往往只有在付诸实践的时机逝去之后，才领悟到人生中最深刻的教训。

In this sentence

①frustration over / at / with sthn.沮丧；懊恼；不满

Synonymsexasperation, annoyance, dissatisfaction, disappointment

原句中为“mutual frustration over export controls”，表示双方因出口管制等未能解决的问题而产生的烦恼、失望与不满情绪。

• Laughter and tears are both responses to frustration and exhaustion. I myself prefer to laugh, since there is less cleaning up to do afterward.笑与泪都是对沮丧和筋疲力竭的反应。我个人更喜欢笑，因为事后需要清理的收拾得更少。— Kurt Vonnegut

②a frustration (to sb)n.令人沮丧的事；挫折

Synonymssetback, headache, irritant, obstacle

• Expectation is the mother of all frustration.期望是所有令人沮丧之事的根源。— Antonio Banderas

③the frustration of sthn.受挫；阻碍；落空

Synonymsthwarting, defeat, disruption, ruin

• The frustration of our hopes often prepares us for a wiser pursuit.希望的落空往往让我们为更明智的追求做好准备。

In this sentence

①mutual + n. (feeling/attitude)adj.相互的；彼此共有的（情感、态度）

Synonymsreciprocal, shared, common

句中修饰 frustration（沮丧、挫败感），表示中美双方对出口管制等贸易问题彼此都抱有同样的挫败感，属于双方相互、共有的感受。

• Love and respect will not endure without mutual trust.没有相互的信任，爱与尊重便无法长久。

②mutual + n. (friend/interest)adj.共同的；共有的（人或事物）

Synonymscommon, joint, shared

• Friendship is a union of spirits, a mutual interest, a partnership in all of life.友谊是心灵的结合，共同的志趣，是贯穿一生的伙伴关系。— William Penn