What does it mean by “add texture squares and value scales” when doing a still life drawing?

Which sentence contains a comma splice? marco rode to school on his bicycle this morning, he arrived an hour early.marco, who enjoys riding his bicycle to school, arrived just before the bell today.marco rode to school on his bicycle on monday, tuesday, and wednesday.marco, who rode to school on his bicycle this morning, arrived an hour early.mark this and returnsave and exit