a
They stimulate maximum root and stem growth at different concentrations.
b
They stimulate maximum root growth and stem growth at the same concentration.
c
They most strongly inhibit root growth at low concentrations.
d
They stimulate maximum stem growth at low concentrations.
a
Based on the given options, the answer would be:
d) They stimulate maximum stem growth at low concentrations.
To determine the correct answer, we need to analyze each statement and understand the role of different concentrations on root and stem growth.
a) This statement suggests that there are different concentrations of some substances that stimulate maximum root growth and stem growth. It implies that the concentration at which maximum root growth occurs is different from the concentration that promotes maximum stem growth.
b) This statement suggests that there is a specific concentration that stimulates maximum growth in both roots and stems. In other words, the optimal concentration for root growth is the same as the optimal concentration for stem growth.
c) This statement suggests that there are certain concentrations at which root growth is strongly inhibited. It implies that low concentrations of some substances negatively affect root growth.
d) This statement suggests that low concentrations of some substances stimulate maximum stem growth. It implies that there is an optimal low concentration at which stem growth is most pronounced.
Based on the explanations above, the correct answer is a) They stimulate maximum root and stem growth at different concentrations.