The roof of the house collapsed due to heavy snowfall; lucky no one was at home when the incident occurred.

Explanation

The sentence has an error in option (b). Here's the corrected versionThe error is in the use of "lucky." "The roof of the house collapsed due to heavy snowfall; luckily, no one was at home when the incident occurred." The correct term here is "luckily," which is the adverb form. It should modify the clause that follows, providing more information about the situation.So, the corrected sentence is: "The roof of the house collapsed due to heavy snowfall; luckily, no one was at home when the incident occurred."