Each answer below describes the connectivity around a single atom.
which answer violates the octet rule (i. e., which one is not a possible bonding configuration for the central atom)?
a. two double bonds
b. three single bonds and one pair of electrons
c. two single bonds and one double bond
d. one single bond and two double bonds four single bonds

d. One single bond and two double bonds.

Explanation:

The octate rule is a chemical rule in which the atoms prefer to have eight electrons in the valence shell. Where a single bond provide two electrons and a double bond provide 4 electrons. Thus:

a. Two double bonds . Two double bonds provide 8 electrons. Octate rule is not violated

b. Three single bonds and one pair of electrons . Three single bonds provide 6 electrons and one pair of electrons provide two electrons. Thus, you have eight electrons and octate rule is not violated

c. Two single bonds and one double bond . Two single bonds provide four electrons and one double bond 4. Thus, you have eight electrons and octate rule is not violated.

d. One single bond and two double bonds. One single bond provides two electrons and two double bonds 8. Thus, you have 10 electrons and octate rule is violated.

e. Four single bonds. Four single bonds provide 8 electrons. Octate rule is not violated.

I hope it helps!

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.