B) Photosynthesis

Here are the answers to your questions:

1) B) Photosynthesis
Photosynthesis is the process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll.

2) B) Iris
The iris is the colored part of the eye that controls the size of the pupil, thereby regulating the amount of light that reaches the retina.

3) D) Skin
The skin is the largest organ of the human body, covering the entire exterior and protecting it from the environment.

4) A) Darwin
Charles Darwin is widely known for his contributions to the science of evolution, particularly his theory of natural selection.

5) A) Digestion
Digestion is the process of breaking down food into smaller molecules that can be absorbed and utilized by the body.

6) B) Chloroplast
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis, containing the pigment chlorophyll.

7) A) Cells
Cells are the basic structural, functional, and biological units of all known organisms, often referred to as the "building blocks of life."

8) B) Kidney
The kidneys are a pair of organs that filter waste products and excess water from the blood, producing urine.

9) A) Adaptation
Adaptation is the process by which organisms adjust to their environment to improve their chances of survival and reproduction.