Suppose Alex considers oranges and apples as perfect substitutes. The price of an orange is $1 and the price of an apple is $2. He is observed consuming only oranges. How many apples could give him the same level of utility as an orange?

1.0.3 apple

2.0.5 apple

3.1 apple

1. Only 2.

2. Only 3.

3. 1. and 2.

4. 2. and 3.

5. 1. and 3.

6. Only 1.

7. 1., 2. and 3.