Answer:
d. no one knows for sure
Explanation:
The universe is infinitely big. It goes on forever and ever, so no one knows what's in it. We might find something really big, but we'll never know if there's something even bigger out there.
Answer:
An example of mutualism is the relationship between remora and shark.
Explanation:
Remora depends on sharks for food and locomotion. It has a sucking mouth that helps it to attach itself to the shark.
When you observe and compare specific physical traits of different birds you will learn that some birds have characteristics that help them live and survive in their own habitat that other birds may not have but make up those birds have characteristics that help them in their own habitat.