What does the disk of a barred spiral galaxy contain? A. globular clusters
B. supermassive black hole
C. spiral arms
D. old stars

What process is believed to be responsible for the formation of the grand canyon? a) diverging tectonic plates b) converging tectonic plates c) erosion over a long period of time d) caving in of the ground due to erosion

Which of these is the most likely way long-term economic growth takes place? a) increases in interest rates b) increases in overall price level c) increases in labor productivity growth d) increases in labor force participation rate

Which of the following types of stars had the smallest initial mass? which of the following types of stars had the smallest initial mass?