Which of the following is a mode of action for pesticides?

Blocking pests' nutrient absorption is a specific and effective mode of action for certain pesticides. This mechanism works by interfering with the physiological or biochemical processes within the pest, ultimately leading to its inability to sustain itself or thrive. When pests are unable to absorb essential nutrients, their growth and reproductive capabilities are significantly hindered, often resulting in their death.

This mode of action is crucial for targeted pest control, as it directly impacts the pest's health through its natural feeding and nutrient assimilation processes. By utilizing pesticides that operate through this mechanism, pest management can be more effective, minimizing harm to non-target organisms and the environment while efficiently controlling pest populations.

The other options do not constitute effective modes of action for pesticides. Changing the color of a pest does not inhibit its function or reduce its population. Similarly, making a pesticide smell more pleasant does not enhance its efficacy or mode of action, nor does increasing its lifespan inherently contribute to its effectiveness in pest control.