Answer: A
Something ephemeral(fleeting, transient) lacks permanence.
Something erratic (unpredictability) lacks predictability.

Answer: A
To be nonplussed (totally at loss) is to exhibit bafflement(perplexity).
To be discomfited(abashed, disconcerted) is to exhibit embarrassment.
To be despicable  is to be worthy of contempt, it not to exhibit contempt.

Answer: D
Thirst is a specific example of a drive (state of instinctual need).
Smell is a specific example of a sense.

Answer: C
Skulduggery or dishonest, unscruplous behaviour is the mark of the swindler.
Chicanery or trickery is the mark of the trickster.

Answer: B
A chameleon, kind of lizard, is studied by a herpetologist(Scientists who studies reptiles and amphibians).
A salmon, a kind of fish, is studied by an ichthyologist.

Answer: C
To ruffle someone's composure is to disturb or trouble his self-possession.
To upset someone's equilibrium is to disturb or trouble his balance.