Summability
可和性
🗣️ 情景例句
Easy does it, tom. don't get all worked up.
冷静点，汤姆，不要太激动。
The student is busy studying math.
这个学生忙于研究数学。
He was just able to lie down on the ground, but could not stand up.
他只能躺在地上，但不能站起来。