单选题 The immune system ______.

A、 used to be unconnected with the brain
B、 causes a lot of stress to people
C、 can be affected by emotional factors
D、 functions independently

【正确答案】 C

【答案解析】第二段说生物学家曾认为the immune system was a separate，independent part of our bodies，但最近研究发现our brain can affect our immune system，而疾病也和情绪有关，据此可以判断情绪能够影响免疫系统。