(Reuters) -Jury selection began on Monday in the penalty phase of the trial of the man who killed 17 students and staff at a Florida high school on Valentine’s Day in 2018, one of the deadliest school shootings in U.S history. Nikolas Cruz pleaded guilty in November to the premeditated murder of 14 students and three members of the staff at Marjory Stoneman Douglas High School in Parkland, about 30 miles north of Fort Lauderdale. A jury will now determine whether the judge should sentence him to life in prison or the death penalty. Broward County Circuit Judge Elizabeth Scherer, who is presidi…