A. The atomic radius of two short period elements a of B is smaller than that of B. the two elements can form compounds with the chemical formula AB2 with positive valence of A A, B may belong to the same cycle B A is the previous periodic element of B C a can only be a metallic element D A may be a group IIA or IVA element in the second cycle Ask for help and explain why, everyone

A. The atomic radius of two short period elements a of B is smaller than that of B. the two elements can form compounds with the chemical formula AB2 with positive valence of A A, B may belong to the same cycle B A is the previous periodic element of B C a can only be a metallic element D A may be a group IIA or IVA element in the second cycle Ask for help and explain why, everyone

Although I don't know how to explain, I also met this question when I was doing my homework. I wrote B, and the teacher gave me a tick. Then I think another answer must be C. I can't write it. I found it here when I looked up this question on the Internet