Explanation:
Since, density is the amount of mass present in per unit volume.
Mathematically, Density = 
As density is directly proportional to mass of a substance. So, more is the density of a substance more will be its mass. And, when more is the mass of a substance then it is likely to sink at the bottom.
Here, it is given that density of oxygen is more than the density of nitrogen. Therefore, balloons filled with oxygen will sink in the air.
On the other hand, balloons filled with nitrogen will rise in the air.
Answer: Group 1 would have the lowest electronegativity values.
Explanation:
Electronegativity is the power of an atom in a molecule to attract electrons. It is also synonymous with the oxidizing ability or non-metallic character of elements.
Generally, across a given period from left to right, electronegativity increases due to increasing nuclear charge and decreasing atomic radius ( or atomic size ). This is because there is a greater tendency for a smaller atom with higher nuclear attraction to attract electrons than a larger atom with a lower nuclear attraction due to the shielding effect of the nuclear attraction by the inner shell electrons on the outermost electrons in the larger atom.
Also, down a particular group, electronegativity generally decreases due to increasing atomic radius/size.
This is why metals are generally electropositive ( lose electrons ) and non-metals are electronegative ( gain electrons ) as they are both found more on the left and right sides of the periodic table respectively.
Choice B the snake is the predator
