题目：People tend to make mistake when ____.
A. they perform. several challenging tasks at a time.
B. new messages are processed one after another
C. their relationships with others are affected
D. the tasks require little thought
喵查答案：A
解析：细节理解题。根据第三段内容，特别是最后一句话可知当人在同时从事两项或多项需要花费精力的工作时，常常会出错。故选择A。
