Generally, when going from left to right across a period on the periodic table:
atomic radii decrease
ionic radii increase
electronegativity decreases
valence electron number decreases

Atomic radio increases as number of valence electrons increase. Hence the first and fourth statement are wrong. Electronegativity is highest for elements on the TOP right hand corner of the periodic table so the third statement is wrong. Hence the answer is the third statement

While unproven, it uses facts to support part of a conclusion. it is still factual and has predictive power, however.