A、 Because livestock production is highly efficient.
B、 Because more people will become wealthier.
C、 Because it may help double food production.
D、 Because it has fewer ecological risks.

【正确答案】 C

【答案解析】解析：信息明示题。由reaching that goal will require major increases in high-efficiency livestock operations for both meat and dairy production．可知，畜牧业是实现粮食翻倍目标的有效方法。故选C。

A、 Balance between human survival and ecology.
B、 Conflict between less land and more production.
C、 Difference between present and future needs.
D、 Calls by environmental critics to consume less meat.

【正确答案】 A

【答案解析】解析：细节推断题。由The challenge is how to ensure food without increasing animal numbers and having an impact on lands and our resource bases．可知，挑战是在不增加动物，不影响土地和资源的基础上保证粮食供应，也即实现人的生存与生态的平衡。故选A。