Step 1: Recall what low specific storage tells us.
Specific storage measures how much water a unit volume of aquifer releases purely from compression of the aquifer skeleton and slight expansion of water under a change in pressure. This release mechanism is the hallmark of confined aquifers, since unconfined aquifers release water mainly by gravity drainage, which gives a much larger specific yield instead.
Step 2: Bring in the transmissivity clue.
Many confined aquifers, especially those made of coarse sand or gravel sealed under a caprock, still transmit water very efficiently, so a high transmissivity value is entirely consistent with a confined system.
Step 3: Compare with perched and leaky options.
Perched aquifers are small, local, and limited in extent, and leaky aquifers involve extra flow through bounding aquitards, neither of which is defined by the pairing of high transmissivity with low specific storage the way a confined aquifer is.
\[ \boxed{\text{Confined}} \]