Evolution

The cranial capacity increased steadily during human evolution.
$Homo\ habilis$: 650–800 cc; $Homo\ erectus$: about 900 cc; Neanderthal man: about 1400 cc; modern $Homo\ sapiens$: about 1350–1450 cc.
This remarkable increase in brain size and complexity is the most apparent change, and it led to intelligence, language, tool-making and culture.
Upright walking, shortening of jaws and loss of body hair also occurred, but they are less marked than the increase in brain size.
Hence the most apparent change is the remarkable increase in the brain size.

(A): wings of butterflies and birds are analogous organs; they are not anatomically similar but perform the same function. Analogous structures are the result of convergent evolution.
(B): Miller passed an electric discharge through $CH_4$, $H_2$, $NH_3$ and water vapour at 800 °C and observed the formation of amino acids. Oxygen was not used (the early atmosphere was reducing) and nucleosides were not the product.
(C): the vermiform appendix is a vestigial organ and an anatomical (morphological) evidence of evolution; 'rudimentary' is not the accepted term.
(D): according to Darwin, evolution took place by small, heritable variations and the survival of the fittest (natural selection). Mutations were proposed by de Vries.
Checking the options, the only one in which both statements are filled correctly is (D) – small variations, survival, together with (A) – convergent.