4. Bob creates his personal profile collage by drawing his favorite things. This is his . A. artistic self
B. social self
C. professional self
D. private self

Engineers find a new metal that is stronger than steel but much lighter. this material is also significantly cheaper than what is currently used for most aircraft, available in large quantities, and easy to manufacture. the engineers are excited because this new material will lower the costs of buying and operating airplanes for companies. what is probably the best step for the engineers to make next?