Earth's surface can change quickly because of?

Which one is best adapted to live in open water in the epipelagic zone, and why? fish a because of its elongated body and powerful tail fish b because of its flattened shape and eyes on the dorsal side fish c because of its streamlined shape and lack of pectoral fins none of these because they are all sedentary

This word for a bug or malfunction was popularized in the 1962 book into orbit by the mercury astronauts

Given: circle a externally tangent to circle b. how many possible common tangents to circles a and b can exist? 2 3 4