How does a client app communicate with Hyperledger fabric chaincode (Smart Contracts)?

A: The app uses an SDK which invokes functionality on the chaincode which then announces the transaction to any peers required to endorse the transaction B: The app uses Hyperledger Composer to communicate with CouchDB which in turn invokes chaincode functionality C: Client apps don’t communicate with Hyperledger fabric directly, they must use Hyperledger Composer for the transmission D: The app points to a node’s IP address, then calls an invoke function on the chaincode address to start the write process