Which of the following factors will cause etiolation in crops?

The factor that causes etiolation in crops is the absence of light. Etiolation is a growth response of plants when they are grown in low light conditions. When plants don't get enough light, they produce less chlorophyll and become pale, elongated, and weak, with long, spindly stems. This is because plants need light to carry out photosynthesis, which is the process by which they make their own food. Without enough light, they cannot produce enough energy to support normal growth, so they grow tall and thin in an attempt to reach more light. The other factors mentioned - low humidity, high humidity, high light intensity, and low temperature - can affect plant growth and development in other ways, but they do not cause etiolation.