One way to represent the solutions shown on the number line at right is $-3\le x<1$. For each number line below, write a similar mathematical sentence to describe the solutions for $x$.  

2. 

   Hint (b):

   Follow the steps in part (a).

3. 

   Hint (c):

   Follow the steps in part (a).

4. 

   Hint (d):

   Follow the steps in part (a).