This is an exception to the general electronegativity trend. It can be explained by looking at the electron configurations of both elements.
<span>Be:[He]2<span>s2
</span></span><span>B:[He]2<span>s2</span>2<span>p1
</span></span>
When you remove an electron from beryllium, you are taking away an electron from the 2s orbital. When you remove an electron from boron, you are taking an electron from the 2p orbital. The 2p electrons have more energy than the 2s, so it is easier to remove them as they can more strongly resist the effective nuclear charge of the nucleus.
I would say the answer is A.
Explanation:
Expression for the
speed is as follows.

where,
= root mean square speed
k = Boltzmann constant
T = temperature
M = molecular mass
As the molecular weight of oxygen is 0.031 kg/mol and R = 8.314 J/mol K. Hence, we will calculate the value of
as follows.

= 
= 498.5 m/s
Hence,
for oxygen atom is 498.5 m/s.
For nitrogen atom, the molecular weight is 0.028 kg/mol. Hence, we will calculate its
speed as follows.

= 
= 524.5 m/s
Therefore,
speed for nitrogen is 524.5 m/s.