Because of these interactions, knowing both parents' blood types lets us predict the relative probability of their children's blood types.

因为这些基因间的相互作用，了解父母双方的血型能让我们预测他们孩子血型的相对概率。

Risk, by contrast, means situations where the relative probabilities are well known: picking a red ball from the first urn, for instance.

与之相反，风险表示相关的概率为人所知的情况：例如，从第一个缸中挑选一个红球。

Various causes could be assigned; but as they are conjectural, and their relative probability cannot be weighed, it would be useless to give them.

可以指定各种原因； 但由于它们是推测性的， 无法权衡它们的相对概率， 因此给出它们是没有用的。