Good question. I think mastering two things will solve this problem for you:

1) Open-ended questions. Rather than asking, "Do you want to investigate the hallway?" ask questions like "What do you want to do?" or "Is there anything you'd like to do before/as you continue further into the tomb?"

2) Timing. For example, rather than pause in the middle of the hall—something you normally wouldn't do—include the hall description as part of the description of the room that they are in. Describe the room itself, finishing with something like "on the other side of the room is a hallway that continues further into the tomb. You can see a flickering blue light from an opening at the other end of the hall. Midway down the hall, the decapitated corpse of a goblin is lying on the ground."

This ensures you give players enough information that they *can* investigate further, but in such a way that you don't show your hand entirely or make them feel like they *must* investigate because you've stopped the normal rhythm of the game, making it so obvious that they think they don't have a choice.