Despite all the hubbub surrounding Elon Musk's cryptic Tesla announcement, we have a week to go until the company lifts the veil on the "D." What is the D, exactly, and what's the other thing Musk mentioned but didn't mention?

According to one analyst, the D may be a truck.

What? You may be thinking. Trucks aren't futuristic. Or sports-car sexy. Maybe not, but there's no denying that trucks are a huge part of the U.S. auto market. So far this year, manufacturers have moved over 1.6 million new trucks off the lot — a 4.4 percent increase over this time last year and more than double the number of mid-sized SUVs. A market this large wasn't going to escape Musk's gaze for very long.

How about the technical challenges?

"In theory, [building an electric truck] is a very demanding thing," said Karl Brauer, a senior analyst at Kelley Blue Book. "When I first heard it, I thought, 'It's silly.'"

Designing an energy efficient truck is hard enough with traditional technology. Everything's heavier compared to a sedan. It needs to be more durable. If you're carrying a load in the back, that raises the power requirements even more. Can Tesla's technology take it? Brauer now seems to think so.

"Under certain circumstances, trucks make perfect sense," Brauer said. "First of all, no one's done an electric truck — and you know how [Musk] loves to be the first do something."

Indeed. In a recent interview with CNN Money, Musk dropped another bombshell: By next year, Tesla vehicles may be capable of doing 90 percent of their travel autonomously. The announcement is a shot across the bow at Google and other manufacturers who've spent years publicly refining their designs.

Here's another reason a truck could make sense: It'd be the perfect tool for small, urban businesses that need to make deliveries within a compact radius of their brick-and-mortar home base.

"A truck with a 120-mile range? If it actually worked for their daily delivery schedule? You're good.

"'D' could stand for 'delivery,'" Brauer joked.

It could also stand for "drive" — as in all-wheel drive, something Musk has hinted may be coming in the Tesla Model S soon.

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