Re: Only a portion of the LM returned to the CM. Why was this method chosen?

For anyone who doesn't know what she means by LM and CM, that's Lunar Module and Command Module.

As to your first question, only a portion of the lunar module returned because it would be impractial and perhaps impossible to return the entire craft to the command module. As you may know, a very important part of planning the manned missions is the fuel aspect. Getting enough fuel into a rocket to carry people up and take them back, while having enough thrust to move all the mass is a hard job. So, fuel is conserved in every way possible; this includes using the least amount of mass possible. That means as the mission continues, the ship becomes smaller and smaller. Now, taking the lunar module down and bringing the whole thing back up would be silly---it couldn't really be reused anyway. [For instance, why lift the landing gear off the surface of the Moon? The LM wasn't going to be re-used, so lifting the landing gear off the surface requires more fuel than just leaving the gear behind.]

Now, the issue of bringing the whole ship down to the surface should be clear. The part of the ship that reaches the moon isn't designed to land or take off, just to transport. The lunar module, however, is made just to get onto the surface. But it's not designed to get back, at least not all of it. So they only took a small part back and used a small part of what they returned to to reach the Earth.