Zynga Inc., the biggest maker of online social games, climbed to the highest price since July on speculation Yahoo Inc. might consider buying the company. Why Yahoo? Its CEO, Marissa Mayer, is seeking acquisitions to bolster the Web portal’s mobile and social capabilities, Wunderlich Securities says. Yahoo has ceded market share in its core business of display advertising amid tough competition from Google and Facebook. Zynga has a market value of about $3 billion.