After World War II, both the United States and the Soviet Union developed space programs. Tensions from the Cold War exacerbated what became known as the “space race.” Each country was determined to reach milestones in space before the other. In 1957, the Soviet Union became the first to launch a satellite, Sputnik 1, into space. The launch was a big surprise to the US. Americans worried they were far behind in space technology and started pushing more funding into aeronautics. In January 1958, the US launched its first satellite, Explorer 1, into space. According to the passage, which of these was true of the Cold War?

A
It occurred before World War II.

B
It ended when the US launched Explorer 1.

C
It started after the Soviet Union launched Sputnik 1 in 1957.

D
It made the competition known as the “space race” more intense.