Answer:
SOD1.
Explanation:
Amyotrophic lateral sclerosis (ALS) may be defined as a type of neurodegenreative disorder in which motor neurons are lost. This disease mainly occur due to mutation in the anti-oxidant enzyme.
Superoxide dismutase type1 (SOD1) is an anti-oxidative enzyme, its mutation may result in the ALS disease. This gene is responsible for damaging oxidative stress in ALS.
Thus, the correct answer is option (a).