respond, responds, respond's or responded?

[Debra Kirk]

One out of every 20 patients (respond, responds, respond’s, responded) to this medication.

Could someone let me the correct word to use in this sentence and what would be the rule for it?

 

[MikeNewYork]

One out of every 20 patients (respond, responds, respond’s, responded) to this medication.

Could someone let me the correct word to use in this sentence and what would be the rule for it?

If this is something learned in the past, as would be the case in a clinical trial, you should use the past tense "responded".

 

[emsr2d2]

Note that "respond's" could never be correct. We don't put apostrophes in verbs.