A:任意砍伐树木
B:适量养殖鱼虾
C:占用耕地建造房屋
D:随意排放生活污水
——Millie,is there anything else you want to know about Yangzhou paper cutting?——Yes,I am still wondering __________ .
把R1和R2串联后接在电压是5V的电源上,通过R1的电流强度是0.2A,R2两端的电压是4V,求R1和R2各等于多少?