According to John Maynard Keynes, Which One of the Following

According to John Maynard Keynes, which one of the following is true about the supply decisions of firms in the short run?

A) Firms are able to supply more output only at a higher price level.
B) Firms are unable to supply more output at any price level.
C) Firms are able to supply any level of output at a given price level.
D) Firms are unable to supply more output at a lower price level.