Apple Inc. has always had a talent for perfecting the work of others. And now, it has the market-defining scale to keep doing that for the foreseeable future.

Still, Apple’s normally festive Worldwide Developers Conference begins Monday under something of a pall. The company’s first quarterly sales decline in 13 years has many people asking whether it will grow again. They also want to know how Apple, with its healthy supply of cash, could make that happen.

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