Concept:Insects damage crops through their feeding actions, mainly by chewing, piercing, and sucking plant tissues.
Explanation:Chewing causes visible damage to leaves, stems, and roots.
Piercing happens when insects insert their mouthparts into plant parts.
Sucking removes sap and essential fluids from the plant.
Grinding is not considered a standard main form of insect damage to crops.
Thus, the listed forms of insect damage are chewing, sucking, and piercing.
Answer:D. chewing, sucking and piercing