A vessel is heading magnetic northwest and
题型：单项选择题
问题：
A vessel is heading magnetic northwest and its magnetic compass indicates a heading of 312°. What action should be taken to remove this error during compass adjustment? （）
A.If the quadrantal spheres are all the way out，replace them with smaller spheres
B.If the quadrantal spheres are all the way in，replace them with larger spheres
C.If the quadrantal spheres are all of the way out，move the spheres in
D.If the quadrantal spheres are all the way out，replace them with larger spheres.
PCl3(气)+Cl2(气) ，反应达到平衡时，PCl5的分解率为20%。则混合气体的密度是氢气密度的倍数是 [ ]