#### Answer

(a) Object B must have the largest mass since object B's acceleration is the smallest.
(b) Object C must have the smallest mass since object C's acceleration is the largest.
(c) $\frac{m_A}{m_B} = 0.6$

#### Work Step by Step

We know that $F = ma$. So;
(a) Object B must have the largest mass since object B's acceleration is the smallest.
(b) Object C must have the smallest mass since object C's acceleration is the largest.
(c) $F = m_A~a_A = m_B~a_B$
$\frac{m_A}{m_B} = \frac{a_B}{a_A}$
$\frac{m_A}{m_B} = \frac{3~m/s^2}{5~m/s^2}$
$\frac{m_A}{m_B} = 0.6$