题目

Each country has many kind people who help to take care of o_1__. For example, some high school and college students in the United States often spend many h__2_ as volunteers in hospitals, orphanages (孤儿院) or homes for the old. They read books to the people in these places, or they just visit them and play games with them or l3__ to their problems.   Other young people volunteers go and work in the homes of people who are sick or old. They paint, clean up, or repair their houses, do their shopping or mow their lawns. For boys who no longer have fathers there is an organization c__4__ B下列说法错误的是（　　）A．如果设“此”为电解质，“彼”为非电解质，不是所有的物质都是非此即彼的B．硅便于运输、贮存，燃烧放出的热量大，将是“21世纪的最佳能源”C．相同温度下，同一化学反应的化学计量系数不同，平衡常数的值可能也不同D．在迄今发现的元素中，不一定所有非金属元素（稀有气体除外）都满足条件“主族元素的族序数≥其周期序数”