Select an appropriate number form in brackets and fill in the blank:Where _____ the shears? (is, are)

Liquids can support neither tensions(张力) nor shears(切力), but they do tend to resist compression(压力).

While not all precipitation-induced downdrafts are associated with critical wind shears, one such downdraft, known as a , is one of the most dangerous sources of wind shear.

如果磁盘损坏，关闭电源。 A: If the disk breaks, stop the supply. B: If the disk bursts, switch off the supply. C: If the disk shears, stop the supply.