Which of the following is true?

a$.$ If formed after a decline, the hammer or inverted hammer indicate bullish reversal pattern.

b$.$ If formed after an advance, the hammer or inverted hammer indicate bullish reversal pattern.

c$.$ If formed after a decline, the hammer or inverted hammer indicate bearish reversal pattern.

d$.$ If formed after an advance, the hammer or inverted hammer indicate bearish reversal pattern.