The second, or B prayer, properly granted, defines the duty of a carrier to a passenger, as approved in Phila. W. B.R. Co. v. Anderson, 72 Md. 519; United Rwys. Elec. Co. v. Hertel, 97 Md. 382, 395; United Rwys. Elec. Co. v. Rosek, 107 Md. 138, 143. The plaintiff's C prayer is the one to which the transit company most seriously objects, and that is to the application of the doctrine of res ipsa loquitur to the facts in this case.