I think you might've forgotten something. There is no labels, pictures, or any options. Add some more stuff and I'd be able to help out.
Not to be too picky, but the question ought to say a positively charge ion rather than atom.
I will assume that is what you mean. An ion, using ordinary means, will be positive if it loses electrons (which are negative).
An ion can never gain protons. Left alone, the nucleus will remain unchanged for the rest of eternity. D is wrong.
C is wrong. If electrons are gained, the ion will go negative.
B is wrong for the same reason D is. An ion can't gain protons and it can't lose them.
A is the answer.
It would 100% be 40 to 50 years old.
to determine whether traits can be inherited independently
Explanation:
the use of dihybrid crosses allowed him to discover the law of independent assortment / discovering that each locus had 2 alleles which segregate during the creation of gametes.
