Question

clues
eins/sehr gut
zwei/gut
drei/befriedigend
vier/ausreichend
fünf/mangelhaft
sechs/ungenügend
rydberg const.
$r_h = r_\infty$
$r_{rydberg} = \frac{m}{m + m} r_\infty$
orbital angular momentum (quantum n. m. z.)
$l^2 = l(l + 1) \hbar^2$
isotope shift
$\
u = \frac{c r_\infty m}{m + m} \left( \frac{1}{n_i^2} - \frac{1}{n_f^2} \
ight)$
was hast du in physik?
vier / ausreichend
fünf / mangelhaft
drei / befriedigend
zwei / gut

Explanation:

Looking at the image, there's a red "A" which typically corresponds to a good grade. The clue "Zwei/gut" (Two/good) is a grade that matches a good performance, and the other options like "vier/ausreichend" (four/sufficient), "fünf/mangelhaft" (five/unsatisfactory), "drei/befriedigend" (three/satisfactory) are lower or less good. Since "A" is a good grade, "zwei/gut" is the most appropriate.

Answer:

D. zwei / gut