Why are conference committees rarely necessary?

Why are conference committees rarely necessary? Conference committees are now rarely used in Congress Senate Resolution 16 is designed to reduce the number of motions necessary to convene a conference committee, [ thus reducing the opportunities for minority obstruction. It seems likely however, that the effects of these changes in the current Congress will be minimal. A conference committee is a committee of the Congress appointed by the House of Representatives and Senate to resolve disagreements on a particular bill. when the two houses pass differing versions of a bill and the first house will not agree to the changes a conference committee will be done. 

The answer is option e.