How does the Rainbow Shark avoid predators?

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.

Several billion years ago which gas was the least prevailant in the atmosphere

What is any method of measuring the age of an object or event in years, such as using atomic half-life?