The number of days in a week is 7. To find the day of the week after 100 days, divide 100 by 7 and find the remainder:
\[
100 \div 7 = 14 \text{ weeks} \text{ with a remainder of } 2
\]
This means that 100 days is equivalent to 14 full weeks and 2 extra days. If today is Monday, then 2 days after Monday is Wednesday.
Answer: Therefore, the day of the week after 100 days is Wednesday. So, the correct answer is option (2).