The answer is "d"!

Seraphim, as described in Isaiah 6:2-6 and Revelation 4:4-8, have 1 face (human, lion, calf, or eagle), human hands, and 6 wings. Some have speculated whether seraphim are a special group within cherubim.

Seraphim are significant for unceasingly praising the Lord ("holy, holy, holy is the Lord"), hovering about the throne of God, or standing before Him. There is perhaps a suggestion that they serve the heavenly court