If two points differing by 1° of latitude and of the same longitude is 110 km apart on the earth, then two astronomical positions on the moon is about A. 10 km B. 25 km C. 30 km D. 50 km

The correct answer is $\boxed{\text{B}}$.

The circumference of the Earth is about 40,075 kilometers. This means that 1 degree of latitude is equal to about 111.3 kilometers. The Moon’s circumference is about 1,737 kilometers. This means that 1 degree of latitude on the Moon is equal to about 30 kilometers.

Therefore, two astronomical positions on the Moon that differ by 1 degree of latitude are about 30 kilometers apart.

Option A is incorrect because 10 kilometers is less than the distance between two points on the Earth that differ by 1 degree of latitude.

Option C is incorrect because 30 kilometers is the distance between two points on the Moon that differ by 1 degree of latitude.

Option D is incorrect because 50 kilometers is more than the distance between two points on the Moon that differ by 1 degree of latitude.