Answer: (b) Because God says, "My name is in him."
Read Exodus 23:20-21
Note: the obvious evidence is found in verse 21 where God says, “Pay careful attention to him and obey his voice; do not rebel against him, for he will not pardon your transgression, for my name is in him.” First, we know only God can pardon us, or not pardon us, if we have hard, unrepentant hearts. Second, the name of God belongs to God only. An ambassador can speak with authority in the name of the one that sent him, but does not have the name nor the authority within himself. In this case, however, God’s name is in the Angel, who is the preincarnate Christ.
Note: Ernest Wendland agrees. In The People’s Bible Commentary: Exodus, he says: “The ‘angel’ that the Lord is sending ahead of his people in their journey is the Lord himself. Israel is to listen to him alone and to honor his Name alone. He will fight their battles for them. He will bring them into their promised inheritance” (143).
Note: In his book Angels: What the Bible Really Says about God’s Heavenly Host Michael Heiser declares (57):
To understand that the angel of Yahweh is Yahweh himself in human form, we must look at what Old Testament scholars call “Name theology” and how these two Yahweh figures are interchanged in the Old Testament. Exodus 23:20–22 is a fundamental passage in understanding the identity of the angel of Yahweh. … On its surface, the description of this particular angel draws interest because this angel seemingly has the authority to withhold forgiveness for the sin of disobedience. The wording is reminiscent of the scene in the Gospels where Jesus claimed that authority. The Pharisees objected: “Who can forgive sins but God alone?” (Mark 2:7; cf. Matt 9:1–8). Their consternation reflected good theology—they were right. As Jesus proceeded to do miraculous acts, he showed that he had such authority, because he was God. The same thought process is applicable to the angel of Yahweh.