D. <span>controlled
is the right answer because a</span><span>n </span>experiment<span> in which an observer tests a hypothesis by looking for changes carried by alterations to a variable.</span>
Ventricular systole is when the ventricles of the heart as the result of electrical activity which helps to pump blood. During ventricular systole oxygenated blood is pumped from the left ventricle through the aortic valve and aorta. Simultaneously deoxygenated blood is pumped from the right ventricle through the pulmonic valve and pulmonary artery to the lungs. Using this explanation blood enters the aorta and pulmonary artery during ventricular systole. <span />
<span>Your skeleton is internal, which means it is contained inside of you. A grasshopper has an external skeleton, or exoskeleton, with everything contained inside it. </span>
The answer is D, carbon dioxide, because carbon dioxide is used in photosynthesis. The answer is not b, glucose, because the end product of photosynthesis is glucose.
