英语语法分析

What factor helps to spread the disease of myxomatosis?

什么因素有助于扩散多发性粘液瘤病毒？

What factor helped to spread the disease of myxomatosis?

什么因素助长了多发性粘液瘤疾病的蔓延？

French physician decided to get rid of the wild rabbits on his own estate and introduced myxomatosis.

一位法国内科医生决定除掉自己庄园内的野兔子，于是引进了这种多发性粘液瘤疾病。