The correct option is B Besides
Options A and B: The words 'beside' and 'besides' are very often confused with each other. But they have completely different meanings.
'Beside' means 'at the side of', whereas 'besides' means 'in addition to'.
For the given sentence, 'besides' is more suitable, as the sentence means:
'In addition to food, we gave the poor some money.'
Hence, B is correct and A is incorrect.
Option C: 'Among' means 'being a part of', 'in the company of'. The word does not relate to the sentence, hence C is incorrect.
Option D: 'Along' is synonymous to 'beside'. (It means that it's similar in meaning.) Both words are not relevant here, hence D is incorrect.