Concept:The Groot Trek was the mass migration of Boers (Dutch settlers) from the Cape Colony to the interior of South Africa.Explanation:The migration involved about 12,000 to 14,000 Boers.They left the Cape Colony to rebel against British policies and to find fresh pastureland.This movement began in 1835 and continued into the early 1840s.Thus, the correct period is from 1835 to 1840.Answer:Option A: 1835/1840.