The answer is C. Recibimos, because its talking about their grandma giving them money and its in first person, so if you say reciben you would be talking about other people reciving money, recibo is in singular meaning one person and nosotros is plural meaning many so it cant be that, and recibe mean he recieves and like I said its a first persona act so the answer would be recibimos which means recieve, this makes the sentence look like NOsotros recibimos el dinero de mi abuela, which means we recieve the money from my Grandma
Hope this helps