Which compound contains both sigma and pi bonds? hccl3 h2co h2s hbr

A pi bond is present wherever there is a double or a triple bond. Single bonds are all sigma bonds. So, the only compound with a pi bond is: 

H2CO

H2CO

Explanation:
H2CO has:
i. two sigma bonds present between each carbon and hydrogen atom
ii. one sigma and one pi bonds present in the double bond found between the oxygen and carbon atoms

The other three compounds have only single bonds, this means that all the bonds are sigma bonds.

Hope this helps :)

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