The place where the electrical current starts, and which is considered the heart's pacemaker, is the...
sinoatrial node,
right atrium,
atrioventricular
Mode, or
left ventricle

Which of the following elements does soil need in the largest quantities to sustain plant life? a. copper b. iron c. nitrogen d. zinc

Which of the following statements about c4 carbon fixation is not true? a c4 carbon fixation is an adaptation for plants exposed to high light intensityb. c4 carbon fixation occurs in more plants than c3 carbon fixation.c c4 carbon fixation is more common in areas of high temperatures than c3 carbon fixation.d. c4 carbon fixation occurs in the inner cells of a leaf rather than the entire leaf.

Which medullary index indicates a human hair? a. 0.653 b. 0.733 c. 0.516 d. 0.256