Final answer:
The time signature of 'Last Christmas' by Cascada is 4/4, where there are four beats per measure and the quarter note gets one beat.
Step-by-step explanation:
The time signature of the song Last Christmas by Cascada is 4/4. Time signatures are notated at the beginning of a piece of music and dictate how many beats are in each measure and which note gets one beat. The song has a steady beat that fits with a 4/4 time signature, where there are four beats per measure, and the quarter note gets one beat. This is a common time signature for many pop songs, making the rhythm easy to follow and dance to.