One way to make lemonade is to start by combining lemon juice and water, then adding sugar to suit your specific desire for sweet- ness. is this combination classified as a compound or a mixture? explain your answer.

The lemonade would be classified as a mixture. A mixture is a system that is made up of two or more of different substances or compounds which are being mixed but the components are not chemically combined. These can be in the form of solutions, colloids and suspensions. Other examples of this would be an aqueous solution of HCl, a mixture of sand and salt and orange juice. Compounds, on other other hand, are systems which are a combination of different elements which are chemically bonded to each other. Examples of this are NaCl in its pure form, calcium carbonate, sugar crystals and water.

The use of piers and beams to build a strong foundation for a house.

Most likely a is the answer - because  you generate   38 atp's but also consume an atp.   each atp gives approx. less than 4 kcal so probably a is the closest answer.