Comparison of organic and inorganic acid strengths
You will be likely be expected to memorize approximate pKa values for different functional groups. Molecules containing protons with lower pKa values are more acidic.

In this case, these are the functional groups you have:


a. alcohol (pKa ~16) 
b. alkyl halide and carboxylic acid (pKa ~4-5)
c. hydrobromic acid (pKa ~-9)
d. carboxylic acid (pKa ~4-5)
e. ammonia (pKa ~35)


I would have to suspect that b is slightly more acidic than d, but they are going to be in similar ball parks. What you're looking for is the most and the least acidic compounds, and the pKas for those compounds are distinct in this question. Since the acidity of a group is inversely proportional to its pKa, the compound with the lowest pKa among its groups is the most acidic and the compound with the highest pKa among its groups is the least acidic. Things get a bit more complicated than that when multiple groups are involved, but this rule usually holds for simple cases.

Hydrobromic acid has the lowest pKa, so it is the most acidic. Ammonia has the highest pKa, so it is the least acidic.