A boat weighs 2 tons, an elephant weighs 1,600 kilograms, a calf weighs 400 kilograms, and a deer weighs 40 kilograms. Which of the three animals can cross the river together by boat?
一艘船载重2吨，大象重1600千克，小牛重400千克，小鹿重40千克，3个动物谁和谁可以一起乘船过河？
<result>3</result>