单选题
Many people are ______ airborne pollutants such as pollen. ______, scientific research has found out that pollen is nutritious for human beings.
【正确答案】
A
【答案解析】句意：许多人对空气传播的污染物过敏，比如说花粉。然而，科学研究发现花粉实际上是很有营养的。be allergic to对…过敏。be indispensable to对…必不可少。be immune to对…有免疫力，可避免…。be vulnerable to易受…的伤害。on the contrary相反，正相反。