Answer the following question given this paragraph: Microtubules , shown in Figure below (a) , are hollow cylinders and are the thickest of the cytoskeleton structures. They are most commonly made of filaments which are polymers of alpha and beta tubulin, and radiate outwards from an area near the nucleus called the centrosome. Tubulin is the protein that forms microtubules. Two forms of tubulin, alpha and beta, form dimers (pairs) which come together to form the hollow cylinders. The cylinders are twisted around each other to form the microtubules. Microtubules help the cell keep its shape. They hold organelles in place and allow them to move around the cell, and they form the mitotic spindle during cell division. Microtubules also make up parts of cilia and flagella, the organelles that help a cell move. Q: What are hollow cylinders and are the thickest of the cytoskeleton structures? Choices: - vesicles - cytoplasm - nucleotides - microtubules A:
microtubules

Answer the following question given this paragraph: Emphysema is a lung disease in which walls of the alveoli break down so less gas can be exchanged in the lungs (see Figure below ). This causes shortness of breath. The damage to the alveoli is usually caused by smoking and is irreversible. Q: What part of the body does emphysema affect? Choices: - bones - brain - heart - lungs A:
lungs

Answer the following question given this paragraph: The reproductive system in both males and females consists of structures that produce reproductive cells, or gametes, and secrete sex hormones. A gamete is a haploid cell that combines with another haploid gamete during fertilization. Sex hormones are chemical messengers that control sexual development and reproduction. The male reproductive system consists of structures that produce male gametes called sperm and secrete the male sex hormone testosterone. Q: What system in both males and females consists of structures that produce reproductive cells, or gametes, and secrete sex hormone? Choices: - circulatory system - immune system - digestion - reproductive A:
reproductive