The correct active/passive form of the given sentence is The teacher told the students that the earth revolves around the sun.

The sentence is in the simple present tense, which is used to describe an action that happens regularly or now. The active voice of the sentence is formed by putting the subject of the sentence before the verb and removing the word "by." In this case, the subject of the sentence is "teacher" and the verb is "tell." So, the active form of the sentence is "The teacher told the students that the earth revolves around the sun."

The other options are incorrect because:

• The teacher said to the students, “The earth revolves around the sun.” This is the original sentence in the active voice.
• The teacher tells the students that the earth revolved around the sun.” This is incorrect because the verb "tells" is in the present tense, but the sentence is about an action that happened in the past.
• The teacher told the students that the earth revolves around the sun.” This is incorrect because the verb "revolved" is in the past tense, but the sentence is about an action that happens regularly or now.
• The teacher told the students that the earth revolve around the sun.” This is incorrect because the verb "revolve" is in the singular form, but the subject of the sentence is "earth," which is plural.