Ozonolysis products of 3,4 - dimethyl hept 3-ene are

•  Alkenes undergo ozonolysis through the oxidative breaking of the double bond. 
• It attacks the provided alkene to create an ozonide while also rupturing the pi and sigma bonds. At intermediate stages zinc dust is used to keep oxygen out because zinc absorbs extra oxygen to make  zinc oxide.

The outcome of this reaction relies on the specific alkene type and double bond position. 

Hence the correct option is (B).