At 45° latitude, the length of one degree of longitude can be calculated using the formula:
\[ \text{Length of 1° of longitude} = 111 , \text{km} \times \cos(\text{latitude}) \]
At 45° latitude:
\[ \text{Length of 1° of longitude} = 111 , \text{km} \times \cos(45°) \]
Since \(\cos(45°) = \frac{1}{\sqrt{2}} \approx 0.7071\):
\[ \text{Length of 1° of longitude} = 111 , \text{km} \times 0.7071 \approx 78.5 , \text{km} \]
It looks like the options provided do not include the correct answer. However, for 1° of longitude at 45° latitude, it is approximately 78.5 kilometers. Since it's not in the options of 444 kilometers, zero kilometers, 222 kilometers, or 55.5 kilometers, please check the calculations or options provided.