Final answer:
The quark structure of a positive pion consists of an up quark and an anti-down quark, resulting in a total charge of +1 elementary charge.
Step-by-step explanation:
The quark structure of a positive pion (pi-plus or π+) consists of an up quark (u) and an anti-down quark (¯d). Positive pions are a type of meson, which means they are particles composed of a quark-antiquark pair. The total charge of the positive pion is +1 elementary charge (e), which comes from the sum of the up quark's +2/3 e charge and the anti-down quark's +1/3 e (the antiparticle of the down quark with charge -1/3 e). Mesons like the positive pion cannot decay into more massive baryons because they possess a baryon number of 0 (quarks have a baryon number of +1/3 and antiquarks have -1/3, canceling each other out).