As temperature is increased gradually from 10 degrees Celsius to 30 degrees Celsius, the rate of reaction of a human enzyme will most likely increase. This is because higher temperatures provide more energy to the enzyme molecules, allowing them to move more rapidly and collide with substrate molecules more frequently. As a result, more substrate molecules are converted into product molecules per unit time, leading to a faster rate of reaction.

However, it is important to note that there is an optimal temperature range for enzyme activity. Beyond a certain temperature (typically around 40-45 degrees Celsius for human enzymes), the rate of reaction will start to decrease as the enzyme begins to denature and lose its structural integrity.