… he switches on the light, the shadow disappears?

Analyze the question

The sentence is: "........ he switches on the light, the shadow disappears." We need a word that connects two events and shows that one happens every time the other does.

Explain the concept

This is a cause-and-effect relationship, often called a "habitual" or "general truth" statement. Words such as whenever, every time and each time join two clauses to show that a result always follows an action. The present simple tense in both clauses ("switches" and "disappears") supports this, because the present simple expresses regular or repeated actions.

Test each option

• A. Whenever: "Whenever he switches on the light, the shadow disappears." This is correct. It means that every time he switches on the light, the shadow goes away.
• B. Expect: "Expect he switches on the light..." This makes no sense. "Expect" is a verb, and the word you probably meant, "except", would not fit either. "Except he switches on the light, the shadow disappears" would say the opposite of what is intended.
• C. Since: "Since he switches on the light, the shadow disappears." "Since" refers to a point in time or gives a reason. It does not describe a repeated event, so it sounds awkward here.
• D. Until: "Until he switches on the light, the shadow disappears." This is illogical. "Until" marks the end point of a continuing situation, and here the shadow disappears after the light comes on, not before it.

Answer

The correct option is A. Whenever.

Exam tip

When both clauses are in the present simple and the sentence describes something that happens repeatedly or as a general rule, look for words like whenever, every time or if. Also check that the sentence still makes sense when you read it aloud with your chosen option.