The correct answer is: A. 143 mm.
The height of the rail for 52 kg rail section is 143 mm. This is the standard height for all 52 kg rail sections, and it is important to ensure that the rails are installed at the correct height in order to ensure safety and proper operation.
The other options are incorrect. Option B, 156 mm, is the height of the rail for a 60 kg rail section. Option C, 172 mm, is the height of the rail for a 70 kg rail section. Option D, 129 mm, is the height of the rail for a 43 kg rail section.
It is important to note that the height of the rail can vary depending on the type of rail and the manufacturer. However, the standard height for a 52 kg rail section is 143 mm.