why option III is wrong?

I. The height of the tallest student is 180 cm.
In the figure, the tallest student is 185 cm.
∴ False

II. The inter-quartile range of the distribution is 15 cm.
Q₁ = 165 cm　　　　　　　Q₃ = 180 cm
The inter-quartile range is Q₃ - Q₁ = 180 - 165 = 15 cm.
∴ True

III. Less than half of the students are taller than 170 cm.
In the figure, half of the students are equal to or taller than 175 cm.
Therefore, at least half of the students are taller than 170 cm.
∴ False

∴ B