Write an awk command that will take a file named list.txt and only print the odd numbered lines. (Do not put the awk code in a separate file, do it from the command line).

a. awk '(NR % 2)==1 {print}' list.txt

b. awk -odd '{print}' list.txt

c. awk 'select odd line {print}' list.txt

d. awk 'NR ~ odd {print}' list.txt

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Suppose the first field of each line is supposed to be an integer. Choose the an awk command that would print out an error message if that field is not an integer.

a. if ($1 !~ /^[0-9]+$/) print "error"

b. if ($1 != /^[0-9]+$/) print "error"

c. if ($1 != /[0-9]+/) print "error"

d. if ($field1 != number) print "error"