• I couldn’t decide which of the two sweaters to buy.

• The saleswoman convinced me to take both.

• At home, I regretted the expensive purchase.

• I vowed to return one of the sweaters.
(combine the above four sentence using complex compound sentence.)

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I couldn't decide which of the two sweaters to buy, but the saleswoman convinced me to take both, and now at home, I regretted the expensive purchase, so I vowed to return one of the sweaters.