While many people think of genetic manipulation of food crops as being aimed at developing larger and larger plant varieties, some plant breeders have in fact concentrated on discovering or producing dwarf varieties, which are roughly half as tall as normal varieties. Which of the following would, if true, most help to explain the strategy of the plant breeders referred to above? ['Plant varieties used as food by some are used as ornamentals by others.', 'Nations with large industrial sectors tend to consume more processed grains.', 'The wholesale prices of a given crop decrease as the supply of it increases.', 'Short plants are less vulnerable to strong wind and heavy rains.']