Trying to identify neutral wire in switch box to use with Wemo Light switch (more than one neutral wire seems to be present)
I see 2 separate circuits in there.  They all share grounds E, which is fine. 

One is the three Romex's left of the "A".  They appear to be mostly "always-hot" except for a switched (receptacle?) on the red wire on the leftmost switch. They use nuts B and C.  

The other is the stuff on the right, partly obscured, and using nuts A and D.  It looks like a power supply comes in the /2 cable, and a probably-light is connected to the /3 cable.  Currently it's wired so the black is always-hot and the red is switched-hot. 

Both sides are doing basically the same thing, delivering always-hot-black and switched-hot red to the /3.   They are clearly demarced, except for nut D being in an odd position due to box cram.  

Whichever circuit you are using the hots from, use the neutrals from that same circuit.   Do not grab the wrong neutral, neutrals must be paired with their hots.  Otherwise if/when you ever upgrade to GFCI/AFCI, you'll have serious problems!