Task: Question Answering
Input (English): Question: Why mechanism produces hyperprolactinemia haloperidol ?: 
 Options:  <1> Blockade of alpha 1 adrenergic receptors. <2> Blockade of alpha-2 adrenergic receptors <3> Blocking of H1 receivers. <4> Blockade of D2 receivers. <5> Blocking of 5-HT2 receptors.
Output (English): 4