碘原子的原子核内带53个单位的正电荷，由此不可能确定的是[ ]
A．质子数
B．中子数
C．电子数
D．核电荷数
答案：B
A farmer with 1,350 acres of land had planted his fields with corn, sugar cane, and tobacco in the ratio of 5:3:1, respectively, but he wanted to make more money, so he shifted the ratio to 2:4:3, respectively. How many more acres of land were planted with tobacco under the new system ？（）
A. 90
B. 150
C. 270
D. 300
E. 450
