For two ratios to be equivalent, its means and extremes if multiplied must be equal to each other.
[tex]\begin{gathered} \frac{a}{b}=\frac{c}{d} \\ ad=bc \end{gathered}[/tex]Let's start with Option A.
[tex]\begin{gathered} \frac{4}{5}=\frac{2}{2.5} \\ 4\times2.5=2\times5 \\ 10=10 \end{gathered}[/tex]Since they are equal, then Option A is equivalent to 4/5.
Let's check Option B.
[tex]\begin{gathered} \frac{4}{5}=\frac{2}{3} \\ 4\times3=2\times5 \\ 12\ne10 \end{gathered}[/tex]Let's check Option C.
[tex]\begin{gathered} \frac{4}{5}=\frac{3}{3.75} \\ 4\times3.75=5\times3 \\ 15=15 \end{gathered}[/tex]Let's check Option D.
[tex]\begin{gathered} \frac{4}{5}=\frac{7}{8} \\ 4\times8=5\times7 \\ 32\ne35 \end{gathered}[/tex]Let's check Option E.
[tex]\begin{gathered} \frac{4}{5}=\frac{8}{10} \\ 4\times10=5\times8 \\ 40=40 \end{gathered}[/tex]FInally, let's check Option F.
[tex]\begin{gathered} \frac{4}{5}=\frac{14}{27.5} \\ 4\times27.5=5\times14 \\ 110\ne70 \end{gathered}[/tex]Hence, only Option A, Option C, and Option E are equivalent to ratio 4/5.