Spring tides refer to the greatest difference in the sea level at high and low tides.

Option 1 correctly describes what spring tides are. These tides occur when the gravitational forces of the moon and the sun align. During spring tides, the high tides are higher than usual, and the low tides are lower than usual, resulting in a greater difference in the sea level between high and low tides.

Option 2 is incorrect because it states the opposite of what spring tides actually are. Spring tides are characterized by a greater difference, not a lower difference, in the sea level at high and low tides.

Option 3 is incorrect because it suggests that there is no difference in the sea level at high and low tides during spring tides. As mentioned earlier, spring tides are characterized by a greater difference in sea level, so this option is inaccurate.

Option 4 is incorrect because it describes the counteraction of the gravitational pull of the sun to that of the moon. While the gravitational pull of the sun does influence tides, option 4 does not accurately describe what spring tides are.

Therefore, the correct answer is option 1.