Increase/decrease forces question

Question

https://i.stack.imgur.com/QNFbc.png

I don't understand why these are marked wrong. THey should be correct. Is the software wrong?

Answer 1

Note that $\bar F_x=\bar F \cos \theta = \bar f_s$.

1. In the first question, if you change the direction to upwards then $\bar F_x$ remains unchanged. Now you increase the angle, then remember that $\cos \theta$ is decreasing on $[0 , \pi]$. Hence $\bar F \cos \theta$ also decreases $\Rightarrow \bar F_x$ decreases.
2. In the second question, use $\bar F_x=\bar f_s$ and the argument we did above. This implies $\bar f_s$ also decreases.