variable inside awk '{print $c}'

i'm trying to do this (in bash darwin);

echo "give me some words: "
read a
c=2 # this is get by other ways
echo $a | awk '{print $c}' # i want to print the column given
# by de $c variable

if there is someone understand what i pretend and see what im doing wrong, please help me.thanks

echo $a | awk -v c=$c '{print $c}' 

or

echo $a | awk '{print $'$c'}' 

awk 'BEGIN { print "Give me some words (Ctrl+C to exit):" }
{ print $c; next }' c=2

thank you man.it works perfectly.