Here is the sentence again:

Watching the Home Shopping Network late one evening, Clarence saw handheld televisions advertised for only $49.99, so he bought ten of them, in his lifetime, Clarence was certain that he would need them all.

The comma between them and in creates a comma splice. At this spot, there are two main clauses joined with a comma alone, making a major error. He bought ten of them is the first main clause. In his lifetime, Clarence was certain is the next main clause.

To fix this problem, you could put a period after them and capitalize the I for in.

Go to the next sentence.

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