How did Sultan Qutb-ud-din Aibak die?

(a) He was treacherously stabbed to death by one of his ambitious nobles

(b) He sustained injuries while besieging the fortress of Kalinjar in Bundelkhand and succumbed tot hem later

(c) He was killed in a battle with Taj-u-din Yildiz, the ruler of Ghazni who entered into a contest with him over the capture of Punjab

(d) He died after a fall from his horse while playing Chaugan