Which of the following reactions gives nitrogen $(II)$ oxide $(NO)$ as one of the products?

• A
  $Cu + \text{dil. } HNO_3 \rightarrow$
• B
  $Cu + \text{conc. } HNO_3 \rightarrow$
• C
  $Zn + \text{dil. } HNO_3 \rightarrow$
• D
  $Zn + \text{conc. } HNO_3 \rightarrow$