Trackballs
(trackball 的复数) n. 追踪球；轨迹球
🗣️ 情景例句
I did both with Richard and Susan,
有Richard和Susan时我这样做，
Suspicion is the poison of true friendship.
猜疑伤害莫逆之交。
the necessary method of study is to group the relevant material and to take note of all possible variant forms and conditions.
应采取的研究方法是，把有关各方面的材料汇集起来，同时注意任何可能出现的异常情况和条件。