A. Average plant height increases with an increase in the concentration of sodium phosphate until the plants reach a maximum possible height.
Explanation:
The graph in the attachment section portrays the average height of plants (cm) on the y-axis plotted against the concentration of sodium phoshate (mg/L) on the x-axis. Based on the observation of the result in the graph, an increase in the concentration of phosphate caused an increase in the average plant height (as depicted by the upward-sloping line).
However, the plant's average height didn't go beyond 35cm despite an increase in concentration of phosphate. This is because the plants has reached a maximum possible height i.e. a height climax. Hence, they cannot grow taller than 35cm no matter the amount of external nutrients (sodium phosphate) supplied.
Therefore, the noticeable trend that can be used to make a conclusion is that average plant height increases with an increase in the concentration of sodium phosphate until the plants reach a maximum possible height.
Based on the scenario being described within the question it can be said that the most likely reason for this misconception would be that the spiral galaxies looked like clouds of gas and dust through telescopes because of their distance from Earth. During that time telescopes were still not as advanced and could only see so much, nowadays they are much more advanced and these galaxies are being analyzed and understood more clearly.
