I believe the correct answers are: A. vibrant colors, B. depictions of moments in time and C. depictions of modern life.
The impressionists didn't use clean and plain colors, but mixed them to produce the effect of quivering and impermanence. They tried to capture single moments in time by placing an emphasis on light, in all of its phases. They also depicted modern life - for example, Renoir's "Dance at Le Moulin de la Galette", Pis.sarro's "Boulevard Montmartre", as well as Manet's famous painting "The Luncheon on the Grass" - all of those paintings depict modern life scenes.
D is not correct. They actually avoided smooth brushwork, leaving the strokes thick and visible.