Which of the following strategies will help you to increase your productivity at work and school?

A. Multi-tasking
B. Setting big goals
C. Focus on your small tasks first
D. Focus on one task at a time

The strategies that will help to increase productivity at work and school are:

B. Setting big goals - Having clear and specific goals in place helps to provide direction and motivation, ultimately increasing productivity.
C. Focus on your small tasks first - Prioritizing and completing smaller tasks before moving on to bigger ones helps to maintain focus, build momentum, and reduce procrastination.
D. Focus on one task at a time - Concentrating on one task at a time improves concentration and prevents distractions, resulting in increased efficiency and productivity.

Therefore, the correct answer would be B, C, and D.