Understanding the Sentence and the Word 'Insensible'

The given sentence is "His broken arm is insensible of feelings." We need to find the most appropriate way to express that the broken arm cannot feel things, which means it lacks physical sensation.

The word "insensible" means:

• Lacking physical sensation; numb.
• Unaware of or indifferent to something.

In the context of a broken arm, "insensible" refers to the lack of physical sensation. The arm cannot feel pain, touch, or other feelings.

Correct Preposition with 'Insensible'

The correct preposition to use with "insensible" depends on its meaning.

• When "insensible" means lacking physical sensation, the correct preposition is to. For example, "His leg was insensible to pain." or "The injured area felt insensible to touch."
• When "insensible" means unaware of or indifferent to something, the preposition can be of or to. For example, "insensible of the danger" or "insensible to criticism."

In the sentence "His broken arm is insensible of feelings," the meaning is clearly about the lack of physical sensation in the arm. Therefore, we need the preposition used when "insensible" means lacking physical sensation.

Analyzing the Options

Let's look at the options provided:

1. No improvement: The original sentence uses "insensible of feelings". Based on the rule for physical sensation, "of" is not the correct preposition here.
2. insensible for: The preposition "for" is not typically used with "insensible" in either common meaning.
3. insensible about: The preposition "about" is also not typically used with "insensible" in this context.
4. insensible to: As explained, "insensible to" is the correct phrase when referring to a lack of physical sensation, which is the meaning needed for a broken arm that cannot feel.

Conclusion

Since the sentence describes a broken arm lacking physical sensation, the correct phrase is "insensible to". This means the arm cannot feel things.

The phrase "insensible of feelings" used in the original sentence is incorrect in this context. Therefore, substitution is required.

The most appropriate substitution is "insensible to feelings".