When building a dialog within the IBM Watson Assistant service, what does the dollar sign $ represent?

A. Shorthand syntax for accessing the dialog context.variable_name.
B. The $ syntax is meaningful when used with the asterisk * for building and utilizing JSON within Watson dialog response

C. Describes replacement of context by user_response within the Watson Assistant dialog

D. Replaces a word or set of words in the position the $ occupies

Reference: https://console.bluemix.net/docs/services/assistant/dialog-build.html#dialog-build