Yes, it is the letter b, that is ▬ ●●● in Morse code.
A mnemonic is to imagine lowercase b with a bolded vertical bar and three dots on the curved part with one dot at each connection to the vertical bar, and another dot at the rightmost point of the curve. The vertical part falls to horizontal position as the curve with dots straighten horizontally. The former curve fades, forming ▬ ●●●.
For the practice:
▬ ●●● u z z
▬ ●●● l ● ▬ c k ●●● ▬ ▬ ●● ▬ ●●●●
● ▬ ▬ ● ▬ ●●● ●●●● ▬ ●●● ▬ ▬ ▬ ● ▬ r ▬ ●●
● ▬ ▬ ▬ ● ▬ ▬ ●●●
▬ ●● r ●● ▬ ●●● ▬ ●●● l ●● ▬ ● g