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Which of the following is true?

1. A silicon wafer heavily doped with boron is a $p^{+}$substrate
2. A silicon wafer lightly doped with boron is a ${ }^{+}$substrate
3. A silicon wafer heavily doped with arsenic is a $\mathrm{p}^{+}$substrate
4. A silicon wafer lightly doped with arsenic is a p ${ }^{+}$substrate