Type of crowding that is genetically determined and is caused by disproportionately sized teeth and jaws:

Type of crowding that is genetically determined and is caused by disproportionately sized teeth and jaws:

A. Primary crowding

B. Secondary crowding

C. Tertiary crowding

D. Environmental crowding

The correct answer is A. Primary crowding. 

Primary crowding refers to a type of dental crowding caused by a genetic discrepancy in tooth and jaw sizes, such as larger teeth relative to the jaw, leading to misalignment. This contrasts with secondary crowding, which results from environmental factors like early tooth loss, and tertiary crowding, which involves late-stage incisor irregularities. Environmental crowding isn't a standard classification but aligns with secondary causes.