Which function clears (writes a 0 to) a bit in a numeric variable?

• A. sizeof()
• B. bitClear
• C. pinMode
• D. #include

Answer: (B)

Clearing a bit means turning a specific bit to 0 while leaving the other bits unchanged. The function bitClear is made for that task: it takes a variable and the bit position you want to zero out, and performs the operation to set that bit to 0. In C/Arduino terms, bitClear(x, n) is like x &= ~(1 << n). For example, if x is 0b10101010 and you clear bit 2, you get 0b10101000. The other options don’t modify individual bits: sizeof() gives the size of a type, pinMode sets a pin’s mode, and #include brings in a header. So bitClear is the right tool for clearing a specific bit.