情态动词can描述太空活动能力 — 英语填空题

宇航员王叔叔在空间站工作。请用 can 或 can't 填空，使短文通顺合理：In space, astronauts ___ float because there is no gravity (重力). But they ___ walk on the floor like on Earth. Wang says, "I ___ move heavy things easily in space because they are weightless (失重的), so I ___ fly like a bird."