In mechanical threshing engineering:
Decreased concave clearance (A): Narrowing the gap between the cylinder rasp bars/pegs and the concave grates subjects grain to severe pinching, impact, and shearing forces, drastically increasing grain breakage/cracking.
Increased feed rate (D): Overfeeding causes choking, high inter-particle friction, and severe mechanical impact inside the threshing drum, escalating mechanical seed damage.
Official NTA key explicitly designates (A) and (D) only (Option 3).
(Note: Very low seed moisture (B) also renders seeds brittle, but in the context of operating machine adjustments, concave clearance and feed rate are primary operational drivers).

A Cotton Picker (Spindle Picker) is a specialized mechanical harvesting machine designed specifically for harvesting seed cotton from open bolls:
It uses rotating barbed spindles to entangle and pull the mature seed cotton lint out of the open burs without damaging the plant foliage or immature unopened bolls.
(Potato uses digger-elevators; maize uses corn snappers/harvesters; forage uses mowers/choppers).

In a reciprocating mower:
Knife registration (centering of knife sections over ledger plates) and cutterbar alignment/lead (setting the outer shoe slightly ahead of the inner shoe to ensure the cutterbar operates perpendicular to the direction of travel under drag load) are the two foundational adjustments required to prevent tearing, reduce draft, prevent clogging, and ensure clean shearing of forage stems.