In a row of girl students facing north, Radhika is $$10^{th}$$ to the left of Purnima who is $$21^{st}$$ from the right end. If Monika who is $$17^{th}$$ from the left end is $$4^{th}$$ to the right of Radhika, how many students are there in the row?

There are 20 girls to the right of Purnima and 9 girls between Purnima and Radhika. Mounika is 17th from the left end and 4th to the right of Radhika. This means that there are 3 girls between Radhika and Mounika, and also, there are 12 girls to the left of Radhika.

The arrangement would be as follows,

(12 girls) (Radhika) (3 girls) (Mounika) (5 girls) (Purnima) (20 girls) 

So, the total number of girls = 12 + 1 + 3 + 1 + 5 + 1 + 20 = 43 girls.

Therefore, the correct answer is option C.