The spring constants of four springs are obtained by plotting the graphs below of force $F$ against extension $x$. Which sequence of graphs shows the spring constants in decreasing order?
- A$2 \rightarrow 1 \rightarrow 3 \rightarrow 4$
- B$3 \rightarrow 4 \rightarrow 2 \rightarrow 1$
- C$4 \rightarrow 2 \rightarrow 1 \rightarrow 3$
- D$4 \rightarrow 3 \rightarrow 2 \rightarrow 1$