Australian AMC 2018 - Junior Question 24

Question 24

In this expression
$$\square\frac13\quad\square\frac14\quad\square\frac15\quad\square\frac16\quad\square\frac17$$
we place either a plus sign or a minus sign in each box so that the result is the smallest positive number possible. The result is

between $0$ and $\frac1{100}$
between $\frac1{100}$ and $\frac1{50}$
between $\frac1{50}$ and $\frac1{20}$
between $\frac1{20}$ and $\frac1{10}$
between $\frac1{10}$ and $1$