Today, shortly after the market closes, Apple (NASDAQ:AAPL) will share an update on its fourth fiscal quarter of 2016. While investors will undoubtedly pay close attention to the quarter's financial results, some of the most interesting nuggets in the update may come from the question-and-answer session following the earnings release. During the conference call, when Apple CEO Tim Cook fields questions from analysts, here are three questions he may be asked.

Apple CEO Tim Cook. Image source: Apple.

1. Where are iPhone sales headed in fiscal 2017?

Investors shouldn't get their hopes up for any product-specific guidance; it's Apple's practice to keep product segment expectations under wraps. But Apple executives have previously given at least some background on potential catalysts for iPhone, and Cook typically provides some color on the important product line from a 10,000-foot view.

In Apple's live earnings call, therefore, look for Cook to update investors on how management is thinking about iPhone -- and possibly even offer a hint as to whether the company expects the key segment to return to growth following the segment's year-over-year declines in both units and revenue in the past two quarters.

Accounting for 57% of Apple's revenue in the tech giant's most recent quarter, the iPhone is integral to the company's overall growth trajectory. Following a 23% year-over-year revenue decline for the segment in Q3, there's good reason for investors to look for some insight.

2. Is services growth sustainable?

Apple's services segment, which according to Apple's financial reports includes "revenue from Internet Services, AppleCare, Apple Pay, licensing and other services," has become increasingly important to the company's results recently. Indeed, for two quarters in a row now, the segment has been Apple's second-biggest when measured by revenue. In addition, revenue in the segment was up an impressive 19% year over year in Q3, making it Apple's fastest-growing segment.

But is this growth sustainable? Look for Cook to provide some insight into this segment's drivers.

3. What's Apple's next frontier?

As Apple faces challenges with growing its largest product segment, investors have wondered where the tech company will turn to next for growth. Many have speculated Apple was readying an electric vehicle -- a move that would obviously open up a new, large market to the company. The secret project was reportedly code-named Project Titan and had been underway for several years. But Apple recently pivoted from aiming to build a car to purely focusing on autonomous-driving software, according to a report from Bloomberg in October.

With Apple reportedly giving up on its plans to build a car, some investors may be wondering if the company has other growth avenues in mind.

Image source: The Motley Fool.

Of course, Apple entered an entirely new segment last year when it started shipping Apple Watch, so wearables is obviously a segment the company is looking to for growth. But with Apple Watch sales still accounting for only a small fraction of total revenue, it's not clear yet if this could grow into a meaningful segment for Apple. Investors should look for some more color on management's expectations for the segment during the conference call.

Apple will announce its fiscal 2016 fourth-quarter results after market close on Tuesday, Oct. 25. On the company's Investor Relations page, investors can tune in to a management's conference call to discuss these results at 2 p.m. PDT (5 p.m. EDT).

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.