A motorcycle consumes 4 liters of gasoline for every 60 kilometers traveled. How many liters are needed to travel 210 kilometers?

The problem states that 4 liters of gasoline are consumed for every 60 kilometers traveled. We need to find out how many liters ($x$) are needed to travel 210 kilometers. We can set up the proportion as:

$$\frac{\text{liters}_1}{\text{liters}_2} = \frac{\text{distance}_1}{\text{distance}_2}$$

Substituting the given values:

$$\frac{4}{x} = \frac{60}{210}$$

$$4 \times 210 = 60 \times x$$ $$840 = 60x$$

$$x = \frac{840}{60}$$ $$x = 14$$

Therefore, 14 liters of gasoline are needed.

The final answer is $\text{C. 14 L}$.