The most accurate comparison/contrast regarding the beliefs of Christianity and Islam among the provided options is:
Christianity and Islam both believe that Muhammad ibn Abdullah was a prophet.
This statement is true in the context that while Christians do not consider Muhammad a prophet; Islam regards him as the final prophet of God. The other statements about the covenant of Abraham are incorrect in how they represent the respective beliefs about the covenant in Christianity and Islam. Christians believe that the covenant is fulfilled in Jesus, while Muslims view the covenant ongoing through their lineage, particularly through Abraham's sons, Isaac and Ishmael.