Which of the following are chiral? (Consider configuration only.)

Each of the first three has a chirality axis with two different groups at each end, the end groups lying in perpendicular planes (for the cyclohexylidene compound the ring end has two faces that differ because the C4 methyl and H lie above and below the plane of the C=C substituents). The plane of the C=C substituents is not a mirror plane because of C4, and the perpendicular plane through the axis would interchange H and COOH, so no mirror plane exists. In 4-methylpenta-2,3-diene one terminus carries two identical CH${}_3$ groups, so a mirror plane exists and the molecule is achiral.