The drug was tested on a group of 50,000 elderly patients who had cancer. The tumors in most of the patients did not respond to the treatment.

The scientists concluded that the drug was not effective in fighting cancer.

What is the most important problem with the design of this investigation?

Which statement is the best summary of the model? a-a series of aerobic and anaerobic reactions take place in cells b- the sun's energy moves through trophic levels in a food chain c-light energy is converted into stored chemical energy plants. d- food molecules are broken down in the cells if living things.

Hairs that clean dirt out of the air in your nasal passages are called: a. sinus b. trachea c. cilia d. mucus

Where is muscle tissue found in the body?