What events led to the German surrender at the Battle of Stalingrad in 1943?

Many of the soldier starved or froze to death, which ultimately led the troop's commander to surrender.

what are the choices? the multiple choices?

i will answer in the comments after the choices have been said.

answer; i believe the correct answer is (4) flip a coin as each participant arrives,heads indicates assignment to the first group: tails indicates assignment to the second group;