The thickness t of a single flat lacing should not be less than

A

$$\frac{1}{30}^{th}$$ length between inner end rivets

B

$$\frac{1}{40}^{th}$$ length between inner end rivets

C

$$\frac{1}{50}^{th}$$ length between inner end rivets

D

$$\frac{1}{60}^{th}$$ length between inner end rivets