A chess problem (need help with analysis) my question is about the position below.

This is, if I copied it correctly, from a book called "How Good Is Your Chess" by Evans.  I'm an amateur so pretty much every single problem is difficult and not the book I had thought it would be but as I was returning this book, I tried another problem in the first few pages, where white is said to have three options:
1.Rac1 2. Rfc1 and 3. Bxf6

We are then told the answer is 3.  I had chosen number 1.  In explaining the answer I had chosen and why it's wrong, he says that if you choose that, then it leads to loss of initiative and endgame:

1 Rac1 Nc5 
2 dxc5 Qxc5+
3. Kh1 Qxg5
4. Qa4 Qa5
5. Qxa5 bxa5

Eventually now we get to my question.  Why do I have to take the black knight on my second move anyways?  What if I just moved my queen to a square defending my knight?  Can I get out of this with a winnable endgame?

2r2rk1/p1qn1ppp/bp1ppn2/6B1/2PP4/PQ1B1P2/1P2N1PP/R4RK1 w - - 0 1
If white does not take the knight on c5 after 1. Rac1, Nc5, the c4 pawn will be lost after 2.Q-somewhere, Nxd3 3.Qxd3, Bxc4. And that is just horrible for white.