What Is the Effective Temperature Range for Plant to Respond $\degree$

What is the effective temperature range for plant to respond to vernalisation, and for how long will a plant typically need to be exposed to this temperature range?

A) -1 $\degree$ C to 4 $\degree$ C for at least 4 weeks
B) 1 $\degree$ C to 9 $\degree$ C for at least 3 weeks
C) -1 $\degree$ C to 9 $\degree$ C for at least 4 weeks
D) 1 $\degree$ C to 9 $\degree$ C for at least 2 weeks
E) -1 $\degree$ C to 9 $\degree$ C for at least 6 weeks