The way i did mine is I left 10 A blank, but I answered 10 B and 10 C. As these are not applicable due to minors age being under 14, it is fine to either answer them or leave it blank. I was suggested by the CIC agent with whom I had a call to ask if I manually write not applicable for 10A, 10B and 10C, I was told by her to leave 10A blank, and answer 10B and 10C based on child requirements. As the child age is under 14, immigration officer will anyways will be skipping these fields... So I did it accordingly.