C is correct answer because in both way algorithm is same.
When a node senses the channel and founds busy then it wait for channel to become free and then it again senses the channel ,if idle then it will send the packet with probability p or else with probability 1-p it will not send the packet.
In other case also ,
When a node senses the channel and founds idle then it will send the packet with probability p or else with probability 1-p it will not send the packet. If it founds busy then it waits for channel to become free.
Both cases are of p persistent CSMA
Reference of both :
1 https://www.tutorialspoint.com/p-persistent-csma-protocol
2 https://www.geeksforgeeks.org/difference-between-1-persistent-and-p-persistent-csma/