Here's a problem to solve: Students want to plant a lemon tree at their school, but the cold winter temperatures in Massachusetts would kill the tree. Which of the following is the best solution to this problem?

Among the 4 following options, which is the correct answer?

- A: planting several lemon trees together in a row
 
- B: building a greenhouse to shelter the lemon tree
 
- C: giving the lemon tree extra fertilizer in the winter
 
- D: tying a stake to the lemon tree for support during the winter
 