The question asks to choose an alternative from the given options that can improve the emboldened part of the sentence. The original sentence is: "He might lose a sense of his superiority which impact his ego in public and private life."

Analyzing the Original Sentence

Let's look at the structure of the sentence. We have "He might lose a sense of his superiority which impact his ego...". The word "which" is a relative pronoun referring back to "a sense of his superiority". Since "a sense" is singular, the verb following "which" should also be in the singular form. The word "impact" is in the base form, which is plural when used with a third-person singular subject in the present tense (e.g., "They impact", but "It impacts"). Therefore, "impact" is grammatically incorrect here; it should be "impacts".

Evaluating the Alternatives

We need to find an alternative that replaces "impact" and improves the sentence, likely by correcting the grammar and fitting the context.

• Bear: This means to carry or support. While grammatically plausible ("which bears his ego"), it doesn't fit the intended meaning in the context of superiority and ego.
• Boosted: This is the past tense of "boost". The sentence uses "might lose," suggesting a potential future or general condition, not a past event. Also, losing superiority wouldn't typically "boost" an ego.
• Candour: This is a noun meaning honesty. It cannot replace a verb like "impact" grammatically.
• Bolsters: This is the third-person singular present tense of "bolster," which means to support or strengthen. Grammatically, "which bolsters his ego" is correct because "bolsters" is a singular verb form matching the singular antecedent "a sense". While losing superiority might not logically "bolster" an ego, the primary improvement here is the grammatical correction of the verb form. Assuming the question seeks a grammatically correct replacement, "bolsters" fits the structure.
• Tolerate: This means to allow or endure. While grammatically plausible ("which tolerates his ego"), it doesn't convey a relevant meaning in this context.

Why 'Bolsters' is the Improvement

Comparing the options, "Bolsters" is the only option that provides a grammatically correct verb form (third-person singular present tense) to replace the incorrect "impact" while also being a plausible verb that can act upon "his ego". Replacing "impact" with "Bolsters" corrects the subject-verb agreement issue ("which bolsters" vs. "which impact"). Even if the overall logical connection between "losing superiority" and "bolstering ego" seems weak, the choice "Bolsters" specifically addresses the grammatical flaw in the original sentence's verb usage.

The improved sentence using the alternative "Bolsters" would be: "He might lose a sense of his superiority which Bolsters his ego in public and private life." This sentence is grammatically sound in its verb usage following "which".