Which of the Following Is an Appropriately Worded Sentence for a Research

Which of the following is an appropriately worded sentence for a research review?

A) Five recent studies have proved that men are less well able to cope with the loss of a spouse than women.
B) The HIV-epidemic has been the cause of considerable anxiety in the gay community.
C) Nurses and physicians struggle with the decision about whether to work in environments where abortion services are offered.
D) Research has consistently found that infant's sleeping position is related to the risk of sudden infant death syndrome.