At times the balance in nature is resulting in a number of possibly unforeseen effects.

问题补充：

At times the balance in nature is , resulting in a number of possibly unforeseen effects.

A. troubled

B. confused

C. disturbed

D. puzzled

答案：

A. troubled

B. confused

(答案→)C. disturbed

D. puzzled

解析：trouble主要指遇上难解决的问题而使人苦恼、忧虑；puzzled指人是困惑的，因此将A、D两项排除；根据句意，自然的平衡本身并不是混乱的（confused）,而不受到了人为的干扰（disturbed）,才会导致不可预见的影响。因此选择C项。