answer to question 19 for paper 1 (2001 ) is cumulonimbus clouds.

(19) The type of Clouds which causes Hail are called
(a) Cumulonimbus
(b) Stratiform
(c) Altocumulus
(d) None of these

What type of cloud would produce hail?
Hail is a form of solid precipitation, which is formed in thunderstorms clouds (Cumulonimbus). Thunderstorms clouds consists of droplets of liquid water (at temperatures lower than 0°С, the droplets can be in a thermodynamically instable supercooled condition) and ice crystals