17. In what lines does the passage compare the size of double radio sources with that of other galaxies? (A) Lines 4-6 (B) Lines 12-14 (C) Lines 19-20 (D) Lines 23-24

20. What is the main idea of the passage? (A) There was great demand for the work of eighteenth-century artisans. (B) Skilled sculptors did not exist in the United States in the 1770's. (C) Many foreign sculptors worked in the United States after 1776. (D) American sculptors were hampered by a lack of tools and materials.