后备: reserve, backup...
经济: economy, economic...
前后: around, from beginning to end, all around, front and rear...
奶粉: powdered milk...
学会: to learn, to master, institute, learned society, (scholarly) association...
寿命: life span, life expectancy, lifetime (of a machine)...
焦急: anxiety, anxious...
微型: miniature, micro-, tiny...
尖: point (of needle), sharp, shrewd, pointed...
大多数: (great) majority...
