A vertical line to the left of multiple staves indicates to play music on all staves at the same time.
Answer: Option A.
Step-by-step explanation:
The five horizontal lines and the four spaces between those lines in any musical instrument is called staves. At the left side of these multiple staves a vertical lines can be found which together creates a system. This system indicates that a music can be played on all these staves.
The five line staves are common, but sometimes musicians prefer staves which are more or even less than five lines. If the note put on the stave is higher, the higher will be its pitch and vice versa.