Which of the following statements about secondary succession is true?
a. secondary succession occurs in ecosystems that have no vegetation.
b. secondary succession affects ecosystems that are already established.
c. ecosystems require pioneer species to undergo secondary succession.
d. secondary succession can occur in areas without soil.

Which best describes the“brain trust” franklin roosevelt promised to make part of his administration? a group of america’s most successful businessmen, who would fix the economya group of hoover’s economic advisers, who would undo previous damage to the economya group of smart advisers, who would assist roosevelt in guiding the nation forwarda group of military veterans, who would assist roosevelt in putting americans back to work