1.Dr. Wang has made much contribution to the theories of modern physics at the ____ of his health.
A.cost
B.disposal
C.mercy
D.expenditure
2.Crisis would be the right term to describe the ___ in many animal species.
A.abolition
B.restriction
C.descent
D.decline
3.Up until that time, his interest has focused almost ___ on fully mastering the skills and techniques of his craft.
A.restrictively
B.radically
C.inclusively
D.exclusively
4.In the ___ of human life the honors and rewards fall to those who show their good qualitiesin action.
A.ring
B.terrace
C.arena
D.ground