Get confused on the merkle tree algorithm
The Stratum server is delivering a partially hashed merkle branch in the response… for which the miner needs to provide, ‘A’ (the generation/coinbase transaction) concatenated with the ‘first’ transaction (B). The remaining elements of the array are ‘pre-computed’ portions of the merkle tree. As indicated on slush’s bitcoin.cz site (http://mining.bitcoin.cz/stratum-mining) “merkle_branch - List of hashes, will be used for calculation of merkle root. This is not a list of all transactions, it only contains prepared hashes of steps of merkle tree algorithm.”

The items returned by the Stratum server for the merkle branch are essentially [b,h(c,d)…] pre-computed to reduce the number of calculations required later to complete the merkle root.