Final answer:
The song that contains the line, "Lets be jolly, deck the halls with boughs of holly" is the traditional Christmas carol called "Deck the Halls".
Step-by-step explanation:
The song that contains the line, "Lets be jolly, deck the halls with boughs of holly" is the traditional Christmas carol called "Deck the Halls". This song is a popular choice for holiday celebrations and is often sung during the Christmas season. In the song, the line is part of the chorus, which goes:
Deck the halls with boughs of holly,
Fa-la-la-la-la, la-la-la-la.