helical A: 圆柱形 B: 螺旋形的 C: 矩形

Helical backbone is held together by _____ between the nearby backbone amides.

Comparing with the spur gears, what are the advantages of helical gears? A: Helical gears operate more smoothly and silently. B: High contact ratio and heavier load capability. C: No thrust along gear axis. D: Less sensitive to undercutting

The representation of left-hand and right-hand cylindrical helical springs are the same. (True or false: 10 points)

The representation of left-hand and right-hand cylindrical helical springs are the same. (True or false: 10 points) A: 正确 B: 错误

The pump has a constant stroke and the amount of fuel delivered is regulated by rotating （） which has a specially arranged helical groove cut into it.

If the cytosine content of double helical DNA is 40% of the total bases, the adenine content would be: A: 10% B: 60% C: 40% D: 30% E: 20%

Compared with standard spur gears, helical gears have advantages of A: Center distance can be adjusted by changing helix angle B: Contact ratio is big with large load capacity C: Transmission is more steady D: Axial force exist