Marco Polo is/was the greatest explorer in the world.

Marco Polo is/was the greatest explorer in the world.
Marco Polo is/was the greatest explorer in the world.

Marco Polo is/was the greatest explorer in the world.
is吧.客观信息.还是看文章的环境.
而且马可波罗是最伟大的探索者这件事情应该是现在才被承认的.
当然如果文章写的是以前的事情,那最好是WAS