Explanation:

- The phenomenon you are describing involves capillary action, where liquid rises in a narrow tube due to surface tension.

- Initially, in a vertical tube, the liquid assumes a certain height \( h \).

- When the tube is inclined, the column height measured along the tube changes but the vertical height \( h \) does not.

- Option 1: The length will not increase. Inclining the tube does not add more liquid or increase the liquid's ability to rise.

- Option 2: The length also doesn't decrease. The column's vertical height is unchanged, and the physical way it holds liquid isn't altered.

- Option 3: Remain unchanged is correct. The true height does not change when inclined, only the measured length changes.

- Option 4: First decrease and then increase is incorrect. The liquid length doesn't fluctuate in such a manner when inclined.

The correct answer is: Remain unchanged.