Which One of the Following Statements Concerning the General Public

Which one of the following statements concerning the General Public License (GPL) is true?

A) The GPL is designed to ensure that the source code of a software remains freely available.
B) The GPL is identical to the BSD license.
C) GPL software may never be sold for money.
D) If you change a program you received under the GPL, you must send your changes to the original author for approval.
E) GPL software may not be used to run nuclear reactors or air traffic control systems.