which type of IS-IS router can an IS-IS Level 1-only router form an adjacency?

With which type of IS-IS router can an IS-IS Level 1-only router form an adjacency?

A.
any IS-IS Level 1 router of any area

B.
any IS-IS Level 2 router of any area

C.
any properly configured IS-IS router

D.
any IS-IS Level 1 router of the same area