下列词语中，没有错别字的一项是( )

Do you play _____ piano in your free time–No, I like sports. I often play _______ chess with my classmates.

汉字积累——下列字形和加点字注音全部正确的一项是（ ）

They weighed the advantages of the operation ______ all the possible risks involved over and over again.

下列描述属于“网络教育”特点的有（）。