What are the threats to internal and external validity?

Step 1 Read the article in Appendix A “Example of a Randomized Clinical Trial” (Nyamathi et al.,2015),Step 2 Discuss the following questions related to the article found on ~p. 162 under Critical Appraisal Criteria:1. Is the type of design used appropriate? Your rationale?2. What are the threats to internal and external validity?3. Is the design appropriately linked to the evidence hierarchy?