Prem and Jamal were answering the question which begins the movie.
Which is to say, their conflicting responses to the cricket question represent how they would answer the opening question about Jamal. Prem says "B", which was "He was lucky" — he thinks Jamal is an ignorant peasant blindly guessing his way through, who doesn't deserve to win. Jamal says "D", which was "It is written". Jamal is right. Salim put twenty million rupees worth of bills into the bathtub where he died.
Probably as a show-off when he gets killed. Immediately after the dance scene, the gang erupts into the empty train station and slaughters Jamal and Latika.
...Or they could have survived since they left the place before it happened. See Harsher in Hindsight in the YMMV page for the reason on this WMG. Salim raped Latika the night that he and Jamal rescued her from Maman.
Its heavily implied but never confirmed that the reason why Salim wanted Jamal out of the room was because that he wanted Latika. After all, earlier he does seem to be attracted to her when she is in dancing for the advert for Maman.- I took it to mean that he was guilting her into being his girlfriend, or more likely, *ahem* "girlfriend", meaning that they did something that would legally be consensual but ethically or philosophically could have been sexual rape.
Salim convinced Latika to have sex with him the night they were rescued to, at least according to him, take away one of her valuable assets.
On her side of the deal, she might unknowingly be lined up to be, basically, a moll, but she would never be a single-use commodity again. On Salim's side of things, he would have something of Latika's that Jamal could never have, even if she said they had never been mutually in love and never been a couple before entering a relationship with Jamal.- But then again, Jamal doesn't care any less about her (on the account of the misfortune she live with), as long as he has her by his side, never to part again.
