In which of the following statements, number ‘three’ is used in ordinal sense ?

The correct answer is I live on the third floor of this building.

Understanding Ordinal vs. Cardinal Numbers:
1. Cardinal Numbers: These numbers indicate quantity or count (e.g., one, two, three). They answer the question "How many?".
2. Ordinal Numbers: These numbers indicate position, order, or rank in a sequential series (e.g., first, second, third). They answer the question "Which position/rank?".

Analysis of Options:
- "This house has three rooms." – Uses 'three' as a cardinal number to count the total number of rooms.
- "All groups have three team members." – Uses 'three' as a cardinal number indicating quantity per group.
- "This box contains many sets of three pencils." – Uses 'three' as a cardinal number referring to the count of pencils in each set.
- "I live on the third floor of this building." – Uses 'third' (the ordinal form of 'three') to indicate the specific rank or positional order of the floor in the building sequence.

Therefore, the number 'three' is used in an ordinal sense in the statement "I live on the third floor of this building."