You are presented with the question "Cells secrete acids and bases to maintain what?" and the following answer choices:  - Chemical energy  - resistance  - increases a body's strength  - To keep their body heat.  - most human enzymes  - aerobic capacity  - allow growth  - temperature  Now knowing that cells secrete acids and bases to maintain the proper pH for enzymes to work and most human enzymes work at a optimal pH of 7.4, but other enzymes work at many different pH ranges, choose the best answer.
most human enzymes

You are presented with the question "what does the digestive system break food into for the body?" and the following answer choices:  - sugar  - fatty  - iron  - lipids  - edible  - liquid  - matter  - Energy  Now knowing that the digestive system breaks food into nutrients for the body and another nutrient to be concerned with is iron, choose the best answer.
iron

You are presented with the question "what can only contract?" and the following answer choices:  - nerves  - Epidermis  - the skin  - strong  - biceps  - Bend  - lungs  - forces  Now knowing that muscles can only contract and muscles in the upper arm called biceps are used to flex the arm, choose the best answer.
biceps

You are presented with the question "where might carbon be stored for million of years?" and the following answer choices:  - In sediment  - stomach  - limestone  - refrigerator  - weathering  - loose dirt  - Earth  - body water  Now knowing that carbon may be stored in sedimentary rock for millions of years and limestone is a type of sedimentary rock, choose the best answer.

limestone