It's hard to predict, my guess will be the latter.

这很难预料，我猜是后者。

普林斯顿公开课 - 国际座谈会课程节选

It's hard to predict.

现在还不清楚，很难预料。

普林斯顿公开课 - 国际座谈会课程节选

The other problem is that as it was passed from me to another individual, to another individual, then the vaccine could change in some ways that were hard to predict because what accumulates in the lesion in my arm is different in some way than what accumulates in the lesion on a cow.

另外一个问题是当疫苗从我这传到另一人,到另一个个体,疫苗可能会发生某些改变,这种改变很难预测,因为胳膊上积累的病变,与牛身上积累的病变是不太一样的

耶鲁公开课 - 生物医学工程探索课程节选