A Mexican police officer tries to grab a migrant, a member of a caravan of thousands from Central America, as they attempt to cross the border into the United States from Tijuana, Mexico, on Sunday. Many among the more than 5,000 migrants in Tijuana were urgently exploring their options amid a growing feeling that they had little hope of making successful asylum bids in the United States or of crossing the border illegally. Most were dispirited Monday, a day after U.S. agents fired tear gas into Mexico to turn back some migrants who had breached the border.   SD-Agencies