Yahoo CEO Marissa Mayer. Yahoo Yahoo's business has been declining for years, and investors are not happy about it.

During Yahoo's annual shareholder meeting on Thursday, one frustrated investor went straight to Yahoo CEO Marissa Mayer to ask about it.

Mayer's answer: The company is investing in growth.

"We're in a very competitive space, so we've invested in our products to make sure that we attract the maximum number of users and the maximum amount of their time and energy each day," Mayer said during the meeting.

She stressed that Yahoo drives most of its revenue through digital advertising, and some parts of the online advertising business, like banner ads, have been in a secular decline over the past few years, as seen in Yahoo's shrinking desktop revenue.

Yahoo has been aggressive on the mobile-advertising front, investing in two major products, Gemini and BrightRoll, to beef up its mobile, native, and video advertisement offerings.

Mayer reiterated that Yahoo's "Mavens" business — short for mobile, video, native, and social — was almost nonexistent when she first joined the company, yet it's now generating $1.6 billion in annual revenue. But Mavens' growth has also turned sluggish in recent quarters.

"These are some of the elements on the strategic plan that we're executing to try and correct for the lack of growth," Mayer said.

She declined to make any comment on Yahoo's core sales process.

But she did say that it was "continuing to make great progress" and that she was "heartened by the interest in Yahoo." Recent reports suggest that companies like Verizon and AT&T and some private-equity firms have expressed interest in buying Yahoo's core internet properties.

"It validates our business progress and achievements to date," Mayer added.