Which of the following is a common cause for the stiffness of rosemary's needles?

The stiffness of rosemary's needles can be attributed to its woody stem structure, which is a characteristic of many perennial herbs. Rosemary belongs to the Lamiaceae family and features an anatomy designed to withstand drought and harsh conditions, enabling it to thrive in its native Mediterranean climate.

The needles of rosemary are more rigid compared to other herbs due to the dense tissues and the presence of lignin, which strengthens the plant's tissues. This structural adaptation allows the plant to retain moisture and maintain its shape over time, reducing water loss and protecting it from environmental stresses.

The other factors mentioned, such as high moisture content or cold storage temperature, do not significantly impact the stiffness of the needles. High moisture content typically leads to a softer texture, while cold temperatures may affect the plant’s overall growth but not the inherent stiffness derived from its woody nature. Exposure to sunlight contributes to the plant's overall health, but it does not specifically confer stiffness to the needles. The woody stem is the primary reason why rosemary has such stiff, resilient leaves.