Babies have shown a strong desire to master the environment very early. Due to the slow development of skills to control movements, their activities are restricted. They do not have enough skills to dominate the environment to survive independently. In this sense, it should be said that they are "Cannot stand-alone". In this passage, what does it mean to say that a baby "cannot stand on its own feet"? ['They cannot survive independently.', 'They cannot control their movements.', 'They have only the will to live independently.', "They don't have enough ability to adapt to the environment."]