Question

1. choose the best answer. found in air and water, __ is the earths most abundant element. iron carbon oxygen chlorine 4. choose the best answer. metalloids have the properties of __ and are elements in the center of the periodic table. noble gases metals only lanthanide elements both metals and nonmetals

Explanation:

• For the first question, oxygen is abundant in air (about 21% by volume) and is a key component of water ($H_2O$). Other elements like iron, carbon and chlorine are not as abundant as oxygen on Earth.
• For the second question, metalloids have properties intermediate between metals and non - metals. They are located along the staircase - like line on the periodic table, not in the center where transition metals are located, and they do not have properties of noble gases or lanthanide elements.

Answer:

1. C. oxygen
2. E. both metals and nonmetals