jmc

First doing the subtraction, we get $$\frac{1}{2}\times \frac{2}{3}\times \frac{3}{4}\times \cdots \times \frac{9}{10}$$ We notice a lot of terms cancel. In fact, every term in the numerator except for the $1$ and every term in the denominator except for the $10$ will cancel, so the answer is $\frac{1}{10}$, or $\boxed{\frac{1}{10}}$ If you don't believe this, then rearrange the factors in the denominator to get $$\frac{1}{10}\times \frac{2}{2}\times \frac{3}{3}\times \cdots \times \frac{9}{9}$$ Everything except for the first term is $1$, so the product is $\text{(A)}\frac{1}{10}$