OFFICIAL EXPLANATION
Following standard police protocol, the police officers demanded that the suspect puts his weapon down.A. that the suspect puts his weapon down
This answer choice is grammatically incorrect. Demand is one of the nine verbs to which the Subjunctive rule applies (if it is followed by that). This means that the next verb after demanded that should be in base form. However, puts is not in base form but rather in present form (V1).
What helps us identify this question as a Subjunctive question as well as identify the mistake is the following Stop Sign:
proposed/recommend/require/request/insist/suggest/mandate/ask/demand that
Whenever you come across this Stop Sign, make sure that the following verb is in its base form.B. that the suspect put down his weapon
Demand is one of the nine verbs to which the Subjunctive rule applies (if it is followed by that). This means that the next verb after demanded that should be in base form - put - as is indeed done in this answer choice.C. that the suspect would put his weapon down
This answer choice repeats the original mistake. Demand is one of the nine verbs to which the Subjunctive rule applies (if it is followed by that). This means that the next verb after demanded that should be in base form. However, would put is not in base form.
What helps us identify this question as a Subjunctive question as well as identify the mistake is the following Stop Sign:
propose/recommend/require/request/insist/suggest/mandate/ask/demand that
Whenever you come across this Stop Sign, make sure that the following verb is in its base form.D. from the suspect to put down his weapon
This answer choice is grammatically incorrect. Demand from someone to do something is an incorrect construct.E. that the suspect put his weapons down
While this answer choice corrects the original mistake and is grammatically correct, it changes the meaning of the original sentence by replacing the singular weapon with the plural weapons.