Explanation:

Microbiome Link to Autism

• It is found that Gut Microbiome composition in humans implicates several diseases, including Autism, Crohn’s disease etc.

• Gut microbiome or gut microbiota, are the microorganisms, including bacteria, archaea, fungi, and viruses that live in the digestive tracts of humans, they affect the body from birth and throughout life by controlling the digestion of food, immune system, central nervous system and other bodily processes.

Autism

• Autism spectrum disorder (ASD) is the term for a group of neurodevelopmental disorders. 

• Researchers are yet to fully understand the aetiology of ASD. However, they are beginning to find that a disorder in the gut-brain axis could have a prominent part.

• Aetiology is the study of the factors that cause a condition or disease.

• It is a complex brain development disability which makes itself visible during the first 3 years of a person’s life.

• It is not mental retardation as people with autism may show excellent skills in spheres like art, music, writing etc. The level of intellectual functioning in individuals with ASDs is extremely variable, extending from profound impairment to superior levels. 

• Causes: There are probably many factors that make a child more likely to have an ASD, including environmental and genetic factors.

• Signs and Symptoms: Children with ASD have impaired social interactions, lack verbal and nonverbal communication skills, and display restricted and repetitive behaviours.

Hence only statement 1st is correct.