Final answer:
The choice between 'which' and 'in which' depends on their role in a sentence. 'Which' introduces non-defining, additional information about a noun, while 'in which' is used when indicating the setting or context related to the noun.
Step-by-step explanation:
The choice between using 'which' and 'in which' depends on the function of the relative clause in the sentence. Generally, 'which' is used to introduce a non-defining relative clause that adds extra information about a noun. On the other hand, 'in which' is used when the relative clause is referring to a situation or context involving the noun, often indicating a place or setting where something happens.
For example:
In number 64, without the specific sentence, it is difficult to provide a conclusive answer. However, typically we'd use 'which' to provide additional information and 'in which' to describe the circumstances surrounding an event.