Option 1 is correct, indicating that both the assertion (A) and reason (R) are true, and furthermore, R accurately explains A.
The assertion (A) states that cattle rearing in Australia is primarily for meat rather than milk. This is true, as Australia is known for its beef export.
The reason (R) states that Australians are traditionally non-vegetarians. This is also true as the Australian diet largely consists of meat.
R correctly explains A because if Australians are traditionally non-vegetarian, it is logical to assume that cattle would be primarily reared for meat. Therefore, the Australians` preference for a non-vegetarian diet would directly impact the purpose of cattle rearing in the country. As such, the reason can effectively explain the assertion. Hence, option 1 is the correct response.