Final answer:
The structure made of protein and lignin by plants to prevent entry by direct penetration is the cuticle, a protective layer that helps in reducing water loss and protecting against desiccation, while stomata manage gas exchange and transpiration. Option A is correct.
Step-by-step explanation:
The structure made of protein and lignin by plants to prevent entry by direct penetration is a cuticle. The cuticle is a complex layer that includes cutin, a waxy substance that is impermeable to water, helping to reduce water loss from the plant to the atmosphere. This protective layer coats the aerial parts of plants, such as leaves and stems, and minimizes desiccation, but it is also impervious to gases including carbon dioxide, which is necessary for photosynthesis.
Stomata are pores found on the leaf surface that regulate gas exchange, including the intake of carbon dioxide and the release of oxygen. These are crucial for maintaining the plant's health since they allow respiration and photosynthesis while controlling water loss through transpiration. Although stomata help in gas exchange, the answer to the structure made of protein and lignin is indeed the cuticle.