Means that the subcommittee might make changes and add amendments before they recommend a bill to the full committee

The answer is Marking . Marking a bill means that the subcommittee could make changes or amendments and add those changes or amendments before recommending a bill to the entire committee. When the subcommittee makes changes and adds an amendment, before recommending a bill to proceed, this is called margin.  

couples could only have one child to reduce the population growth.