Select the word that names a necessary part of the word given below. harvest

Concept: an "essential part" item asks which of the listed words names something the given word cannot do without. The test is necessity, not association — a word that merely accompanies the idea in time, assists it with equipment, or follows it as a later step is optional and fails; only what the definition itself must contain passes.

Application: to harvest is to gather in matured agricultural produce, and as a noun a harvest is the produce so gathered. Take that definition apart and one element cannot be removed — the produce, that is, the crop. With no crop there is nothing to gather and no harvest exists, whatever the season, whatever the equipment, and whatever becomes of the yield afterwards.

Cross-check: test each listed word against that necessity requirement.

• autumn — reaping is tied to when a plant matures, not to a fixed season: in India rabi wheat is cut in March–April while kharif rice is cut in October–November, and in the southern hemisphere the grain gathering falls around December. The timing varies, so it is not required.

• stockpile — storing produce is a step that may follow the gathering, but produce sold at the field gate or eaten straight away has still been gathered in. Storage is optional.

• tractor — machinery speeds field work, yet a field reaped by hand with a sickle has still been gathered in. Equipment is optional.

• crop — take the produce away and the act has no object at all, while each of the other listed words can be taken away and a gathering-in still takes place.

Result: only crop survives the necessity test, so crop is the essential part of harvest.