Explanation:

- Indifference Curve Overview: An indifference curve represents a set of bundles of goods between which a consumer is indifferent. That means the consumer has no preference for one bundle over another.

- Option 1 - Concave to the origin: This is incorrect. Indifference curves are not generally concave; they tend to show a diminishing marginal rate of substitution.

- Option 2 - Convex to the origin: This is the correct answer. Indifference curves are typically convex, reflecting diminishing marginal rates of substitution as one moves along the curve.

- Option 3 - L-shaped: This form is characteristic of perfect complements, not standard indifference curves.

- Option 4 - A vertical straight line: This could depict a situation with zero substitution between goods — where only vertical combinations are valued, but this is atypical for standard indifference curves.