In a knock-out tournament, each match results in the elimination of one team, except for the final match that determines the champion. For 21 teams, the number of matches required to determine the winner can be calculated as follows:
To find the total number of matches in a knockout tournament, we consider:
Thus, the total number of matches played, including the third-place match, is:
Total matches = 20 (to find the winner) + 1 (third-place match) = 21 matches
Therefore, the correct answer is 21.

Rearrange the following parts to form a meaningful and grammatically correct sentence:
P. that maintaining a positive attitude
Q. even in difficult situations
R. is essential for success
S. and helps overcome obstacles effectively
Rearrange the following parts to form a meaningful and grammatically correct sentence:
P. a healthy diet and regular exercise
Q. are important habits
R. that help maintain good physical and mental health
S. especially in today's busy world