“trust.” To properly understand “trust” in this verse, see the commentary on 1 Corinthians 12:9, “trust.”
“this mountain.” Jesus was on the Mount of Olives, where both Bethany and Bethphage were.
“snatched up.” The Greek is airō (#142 αἴρω; pronounced eye-rō), and it is passive voice, imperative mood. Although it would be very literal to say, “Be taken up,” the imperative mood combined with the context, moving a mountain at your command, gives the sense that the mountain is being snatched up out of its place and thrown into the ocean.
“doubt.” See commentary on Mark 11:23.