You need to sharpen your eyes in doing experiments.
v.伸展，伸长(pull taut, expand)
She stretched herself out on the couch and fell asleep.
A fresh coat of paint can transform a room.
n.平衡(balance) ; 稳定
Social stability is key to economic growth.
v.（使）收紧；压缩 (reduce, compress)
The snake constricted its body around its prey and killed it
Plastic bags contract when being heated.
vt.缩减 (cut back, reduce)
The discussions were curtailed when the fire alarm went off.
vi.去掉；减损 (lessen, derogate)
Their argument detracted from the otherwise pleasant conversation.
Unexpected expenses diminished the size of my bank account.
The stream will continue to dwindle if it doesn't rain.