The author of this passage is proposing to resolve the problem of political radicalism in the United States by

A. deporting those sympathetic to Bolshevism.
B. identifying Russian and German immigrants.
C. having tighter restrictions on the press.
D. declaring radicals to be criminals.

D. declaring radicals to be criminals.

To determine the answer to this question, we need to analyze the information provided in the passage. Let's break down each option and evaluate if the author proposes it as a solution.

A. Deporting those sympathetic to Bolshevism: The passage does not mention specifically deporting individuals sympathetic to Bolshevism.

B. Identifying Russian and German immigrants: The passage does not mention identifying specific nationalities as a solution to political radicalism.

C. Having tighter restrictions on the press: The passage does not mention tightening restrictions on the press as a proposed solution to political radicalism.

D. Declaring radicals to be criminals: The passage does not explicitly state this proposition either.

After evaluating all the options, none of them are directly proposed by the author as a solution to political radicalism. Therefore, without more context or information, we cannot determine the correct answer based on the passage provided.

Based on the information provided, the author of the passage does not explicitly propose any of the options listed. It is important to note that the passage's author's perspective or proposed solution might not be explicitly mentioned in the given information.