At temperatures higher than the maximum growth temperature for an organism: a. proteins are permanently denatured. membranes become too fluid for proper function.
b. hydrogen bonds within molecules are broken.
c. hydrogen bonds are broken and proteins are permanently denatured.
d. hydrogen bonds are broken, proteins are denatured, and membranes become too fluid.

The correct answer is option d, that is, hydrogen bonds are broken, proteins are denatured, and membranes become too fluid.

Explanation:

The maximum growth temperature refers to the highest temperature at which growth can take place. Let us take an example of bacteria, it is found that each bacterial species possess a requirement of specific growth temperature, which is mainly determined by the requirement of the temperature of its enzymes. Each of the organism exhibits an optimum growth temperature, a minimum growth temperature, and a maximum growth temperature.  

When for an organism, the temperature goes more than its maximum growth than it results in the dissociation of the hydrogen bonds, denaturation of the proteins, and even the membranes become too fluid. This can even result in the death of the species. However, there are some of the organisms, which can thrive high temperatures known as thermoduric organisms, but they fail to grow effectively at such temperatures.  

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.