下面哪个数最接近 1？

1. Calculate the difference between 1 and each given number.

Difference for (1) $0.85$: $1 - 0.85 = 0.15$
Difference for (2) $0.93$: $1 - 0.93 = 0.07$
Difference for (3) $1.05$: $1.05 - 1 = 0.05$
Difference for (4) $2.09$: $2.09 - 1 = 1.09$

2. Compare the differences to find the smallest one.

Comparing the differences: $0.05 < 0.07 < 0.15 < 1.09$.
The smallest difference is $0.05$, which corresponds to $1.05$.