a : a shrub or herb grown with an erect main stem to ensure that it types or resembles a tree b : a fruit tree grafted on a stock that does not induce dwarfing知乎，让每一次点击都充满意义 —— 欢迎来到知乎，发现问题背后的世界。Healthier Household Ecosystem: By removing dust and allergens, we produce a much healthier