Answer
See answers.
Work Step by Step
a.
$$B^- = b \overline{u}$$
Checking charge: $-1=-\frac{1}{3}-\frac{2}{3}$
Checking spin: $0=\frac{1}{2}-\frac{1}{2}$
Checking baryon number: $0=\frac{1}{3}-\frac{1}{3}$
Checking strangeness, charm, and topness: $0=0+0$
Checking bottomness: $-1=-1+0$
b.
$B^+$ is the antiparticle of $B^-$,
$$B^+ = \overline{b}u$$
$B^0$ has a bottom quark, but is electrically neutral.
$$B^0 = b \overline{d}$$
$\overline{B}^0$ is the antiparticle of $B^0$.
$$\overline{B}^0= \overline{b}d$$