Answer:
The symbol used to indicate that the syllable "so" is stressed is "só".
Step-by-step explanation:
In the word "so", the "o" is the vowel sound that is pronounced with more emphasis or force. In order to indicate that the syllable "so" is stressed, the symbol "´" is placed over the vowel "ó". This symbol is called an acute accent, and it is commonly used in Spanish and Portuguese to indicate stress on a syllable. Therefore, the correct symbol over the syllable "so" to indicate that it is stressed is "só".