By MICHELLE CHAPMAN and TOM KRISHER (AP) — Tesla CEO Elon Musk has acquired a 9% stake in Twitter to become its largest shareholder while joining other critics in questioning the social media platform’s dedication to free speech and the First Amendment. Musk's ultimate aim in acquiring 73.5 million shares, worth about $3 billion, isn't clear. Yet in late March Musk, who has 80 million Twitter followers