Answer: Option B (It will speed up, because the rate of transpiration will increase).
Step-by-step explanation:
An increased temperature of 100 degrees will speed up the rate of movement of water through plant. Plants through their stomata in the leaves, lenticels in the stem and the cuticle of leaf surface tends to loose more water to that extrinsic environment.
Hence, increase in temperature is directly proportional to increase in transpiration. While decrease in temperature gives rise to low transpiration rate.