A. There is no payload option in MCS that guarantees delivery. You need to find a different way to implement your requirement.

B. You send individual notifications to APNs, GCM, and WINS, and use the "alert" keyword in the message.

C. You define the message payload by using the MCS template and utilize the "alert" keyword in the message.

D. You send a unified payload object that addresses the APNs, GCM, and WINS services, and use the
"alert" keyword in the message.