Lactic acid fermentation is a metabolic process that occurs in certain microorganisms, such as bacteria and yeast, where glucose is converted into lactic acid. This process is an anaerobic pathway, meaning it takes place in the absence of oxygen. Lactic acid fermentation is commonly observed in the production of certain foods and beverages, such as yogurt, sourdough bread, and sauerkraut.

Let's analyze each option and understand why option A is the correct answer:

a) Shows slow oxidation of NADH to NAD:
During lactic acid fermentation, glucose is broken down into two molecules of pyruvate through glycolysis. In this process, NADH, which is an energy-rich molecule, is oxidized back to NAD+. This oxidation is relatively slow compared to other metabolic pathways, such as aerobic respiration. As a result, NADH is not fully oxidized, and its energy is captured in the form of lactic acid. This slow oxidation of NADH to NAD is a characteristic feature of lactic acid fermentation.

b) Occurs with the help of hetero-fermentative Lactobacillus:
Hetero-fermentative Lactobacillus is a type of bacteria that is involved in lactic acid fermentation. However, it is not the only microorganism capable of carrying out this process. There are various other bacteria and yeast species that can also perform lactic acid fermentation. Therefore, this statement is not entirely accurate.

c) Always releases CO2:
Lactic acid fermentation does not always release carbon dioxide (CO2). The production of CO2 is dependent on the specific microorganism involved in the fermentation process. Some microorganisms, such as yeast, produce CO2 as a byproduct during fermentation. However, many bacteria involved in lactic acid fermentation do not produce CO2. Therefore, this statement is incorrect.

d) Is not hazardous:
Lactic acid fermentation is generally considered safe and not hazardous. It is a natural process that has been harnessed by humans for centuries in the production of various foods and beverages. However, it is important to note that in certain conditions, lactic acid fermentation can lead to spoilage of food products. This can occur if the fermentation process is not properly controlled or if harmful microorganisms contaminate the fermentation environment. Overall, lactic acid fermentation is a safe and widely utilized process.

In conclusion, the correct answer is option A, as lactic acid fermentation indeed shows slow oxidation of NADH to NAD. The other options are either incorrect or not entirely accurate.

Lactic acid fermentation is hazardous and may release CO₂.