Fill in the blank with most appropriate word.

I am sorry to ______ on you at this late hour.

intrude

The most appropriate word to fill in the blank is intrude.

The word intrude means to come into a place or situation where you are not wanted or welcome. In this case, the sentence is saying that the speaker is sorry to intrude on the listener at this late hour. This means that the speaker is sorry to be bothering the listener at this late hour, when the listener may be busy or asleep.

The other options are not correct.

• Instruct means to give someone orders or directions. It cannot be used in this sentence because it does not mean to bother or inconvenience someone.
• Interfere means to meddle in someone else's affairs. It can be used in this sentence, but it would mean that the speaker is trying to control or influence the listener's actions.
• Interrupt means to break into someone's conversation or activity. It cannot be used in this sentence because it does not mean to bother or inconvenience someone.