What is the current limitation in the research findings to date regarding ALS?

What is the current limitation in the research findings to date regarding ALS?

1. Funding is insufficient to continue this aspect of the research.

2. There are very few people who are faced with the disease to study.

3. The study has not had enough time to draw any correlations between gene mutation and ALS.

4. The mutation that has been studied accounts only about two percent of the instances of ALS.What is the current limitation in the research findings to date regarding ALS?
What class has handed you this homework question?What is the current limitation in the research findings to date regarding ALS?
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