Which of the following statements accurately describes the early history of digital recording?

a) In the 1960s, Japan conducted experiments with digital recording but it was not until the 1980s that digital audiotape was widely used.
b) In the 1960s, Japan conducted experiments with digital recording and it quickly became widely used.
c) In the 1960s, the United States conducted experiments with digital recording but it wasn’t until the 1980s that digital audiotape was widely used.
d) In the 1960s, the United States conducted experiments with digital recording and it quickly became widely used.