The Great Gatsby, blankly

Could you please tell me if "blankly" in this excerpt from the chapter Five of The Great Gatsby means "without expression" or rather "with confusion", "uncomprehendingly"?

“Is everything all right?” he asked immediately.

“The grass looks fine, if that’s what you mean.”

“What grass?” he inquired blankly. “Oh, the grass in the yard.” He looked out the window at it, but, judging from his expression, I don’t believe he saw a thing.

Thank you.