To solve this problem, we need to identify which cells are responsible for producing the myelin sheath.$\newline$Let's analyze each option:$\newline \bullet$Option 1: Astrocytes and Schwann cells.$\newline$ - Schwann cells are indeed responsible for producing the myelin sheath in the peripheral nervous system (PNS).$\newline$ - However, astrocytes do not produce myelin; they are involved in supporting neurons and maintaining the blood-brain barrier.$\newline$ - Therefore, this option is incorrect.$\newline \bullet$Option 2: Oligodendrocytes and osteoclasts.$\newline$ - Oligodendrocytes are responsible for producing the myelin sheath in the central nervous system (CNS).$\newline$ - Osteoclasts are involved in bone resorption and have no role in myelin production.$\newline$ - Therefore, this option is incorrect.$\newline \bullet$Option 3: Osteoclasts and astrocytes.$\newline$ - As mentioned earlier, osteoclasts are involved in bone resorption, and astrocytes do not produce myelin.$\newline$ - Therefore, this option is incorrect.$\newline \bullet$Option 4: Schwann cells and oligodendrocytes.$\newline$ - Schwann cells produce the myelin sheath in the PNS.$\newline$ - Oligodendrocytes produce the myelin sheath in the CNS.$\newline$ - Therefore, this option is correct.$\newline$Thus, the correct answer is Option 4: Schwann cells and oligodendrocytes.