题目

Watching television more than two hours a day early in life can lead to attention problems later in adolescence, according to a study released on Tuesday.      The roughly 40 percent increase in attention problems among heavy TV viewers was observed in both boys and girls The link was established by a long-term study of the habits and behaviors of more than1,000 children born in Dunedin, Hew Zealand, between April 1972 and March 1973.      Those who watched more than two hours, and particularly those who watched more than three hours, of television per day during childhood had above-av用NA表示阿伏加德罗常数，下列的叙述正确的是(    )A.在2 L 0.15 mol·L-1 K2SO4溶液中，含有K+和的总数为0.9NAB.在标准状况下46 g NO2含有NA个分子C.a g某气体含有分子数为b，则c g该气体在标准状况下的体积是22.4bc/aNA LD.当稀硝酸跟5.6 g Fe反应完全时，电子转移一定是0.3NA