ht",     (string) Selected statistic
       "time",       (string) Selected statistic
       ...
     ]

Result:
{                              (json object)
  "avgfee" : n,                (numeric, optional) Average fee in the block
  "avgfeerate" : n,            (numeric, optional) Average feerate (in satoshis per virtual byte)
  "avgtxsize" : n,             (numeric, optional) Average transaction size
  "blockhash" : "hex",         (string, optional) The block hash (to check for potential reorgs)
  "feer