Why do we have to ________ Joan’s selfish behavior? She should learn to care for others.

A．keep up with

B．catch up with

C．put up with

D．come up with

农田作物的生长和土壤养分之间有着密切的关系，其产量往往受土壤中供应最不足的营养元素所制约。这是( )

A．李比希最小因子定律
B．谢尔福德耐性定律
C．阿伦法则
D．贝格曼法则