Of course I believe it was Moses and Elijah ! It is written . You just read it. ( God is not the God of the dead, but the living. MARK 12:27; LUKE 20:38; MATTHEW 22:32 kjv)
Mark 9:
2 And after six days Jesus taketh with him Peter, and James, and John, and leadeth them up into an high mountain apart by themselves: and he was transfigured before them.
3 And his raiment became shining, exceeding white as snow; so as no fuller on earth can white them.
4 And there appeared unto them Elias with Moses: and they were talking with Jesus.
5 And Peter answered and said to Jesus, Master, it is good for us to be here: and let us make three tabernacles; one for thee, and one for Moses, and one for Elias.
6 For he wist not what to say; for they were sore afraid.
7 And there was a cloud that overshadowed them: and a voice came out of the cloud, saying, This is my beloved Son: hear him.
Matthew 17:
Matthew 17
King James Version (KJV)
17 And after six days Jesus taketh Peter, James, and John his brother, and bringeth them up into an high mountain apart,
2 And was transfigured before them: and his face did shine as the sun, and his raiment was white as the light.
3 And, behold, there appeared unto them Moses and Elias talking with him.
4 Then answered Peter, and said unto Jesus, Lord, it is good for us to be here: if thou wilt, let us make here three tabernacles; one for thee, and one for Moses, and one for Elias.
5 While he yet spake, behold, a bright cloud overshadowed them: and behold a voice out of the cloud, which said, This is my beloved Son, in whom I am well pleased; hear ye him.
6 And when the disciples heard it, they fell on their face, and were sore afraid.
7 And Jesus came and touched them, and said, Arise, and be not afraid.
8 And when they had lifted up their eyes, they saw no man, save Jesus only.