Final answer:
The debatable claims are the first two statements about the United States needing to welcome immigrants, or limit them, for economic competitiveness. They are subject to debate and interpretation, unlike the two statements that are historical facts.
Step-by-step explanation:
The debatable claims among the options provided are:
- The United States must remain a country that welcomes immigrants if it wishes to remain economically competitive.
- The United States must drastically limit immigration if it wishes to remain economically competitive.
These are debatable because they represent opposing viewpoints on the issue of immigration's effects on economic competitiveness. Both statements are open to interpretation and can be argued from various economic, social, and political perspectives.
In contrast, the statement about John F. Kennedy writing a book called A Nation of Immigrants, which was published in 1964, is not debatable as it is a historical fact. Similarly, the statement regarding President Barack Obama's description of the United States as 'a nation of immigrants' is also not debatable as it represents a direct quote and an expression of sentiment rather than a claim or argument potentially open to debate.