Answer
(a) $ f, c, e, d$
(b) $b, a$
(c) $c \parallel d$ and $d \parallel f$
(d) $b \perp f$ and $b \perp d$
Work Step by Step
(a/b) Lines where y increases as x increases have positive slopes $\rightarrow c, f, d, e$ while those where y decreases as x increases have negative slopes $\rightarrow a, b$
(c) Lines that appear to never intersect even when extrapolated are have equal slopes and are said to be parallel $\rightarrow c \parallel d$ and $d \parallel f$
(d) Lines that intersect at right angles are deemed orthagonal or perpendicular $\rightarrow b \perp d$ and $b \perp f$
