Question

if necessary, adjust the verb(s) below to fix any matching errors.
original quote:
the researchers found that taking vitamin d decreased symptoms of sunburns compared with taking a placebo, and this effect increased in proportion to how much was consumed.
a recent study suggests that vitamin d can make sunburns less painful and that the positive impacts of the vitamin \ increased in proportion to how much is consumed.\

Explanation:

The original quote uses "increased" in the past tense. However, the verb tense in the second part of the sentence should match the present - tense context set by "suggests" in "A recent study suggests...". So, "increased" should be changed to "increase" to maintain tense consistency.

Answer:

increase