Final answer:
The isoquants for inputs that are perfect complements consist of a series of right angles.
Step-by-step explanation:
The correct answer to the question is 1) right angles.
The isoquants for inputs that are perfect complements to each other consist of a series of right angles. In this case, inputs are used in fixed proportions, meaning that they are always used in a specific ratio to each other.
For example, let's say we have inputs A and B, and they are perfect complements with a fixed proportion of 1:1. In this case, all the combinations of input A and input B that result in the same level of output will form a right angle. If we increase input A or input B without changing the ratio, we will not be able to increase the level of output.