As Arc is a part of Circle similarly segment is a part of line.

(A) Something that is plain is the opposite or ornate – the former means simple, the latter means fancy. Similarly, austere and luxurious are opposites – something austere is plain and severe, something luxurious is rich and comfortable.
ORNATE: showy or flowery, as some literary styles
Austere: having a severe or stern look, manner, etc.; forbidding
Obvious: easy to see or understand; plain; evident
Embellished: to improve (an account or report) by adding details, often of a fictitious or imaginary kind; touch up
Garish: gaudily or showily dressed, decorated, written, etc.
Gaudy: bright and showy, but lacking in good
taste; cheaply brilliant and ornate

(D) To gorge oneself is to eat, or ingest, without restraint (think of Thanksgiving dinner). To guzzle is to drink, or imbibe, without restraint.
INGEST: to take (food, drugs, etc.) into the body, as by swallowing or absorbing
GORGE: the crop or stomach of a hawk
Devour: to eat or eat up hungrily, greedily, or voraciously
Swallow: any of various birds resembling swallows, as certain swifts
Engulf: to swallow up; overwhelm
Grasp: to take hold of firmly with or as with the hand or arms; grip
Seize: to take hold of suddenly or forcibly, with or as with the hand; clutch
Imbibe: a) to drink (esp. alcoholic liquor) b) to take in with the senses; drink in
Guzzle: to drink (or, rarely, eat) greedily or immoderately
Respire: to breathe or carry on respiration; inhale and exhale air

(B) A roadblock stops travel from taking place (at least along that particular path); an impediment is an obstacle that prevents progress from being made.
Detour: a route used when the direct or regular route is closed to traffic
Impediment: [Now Rare] an impeding or being impeded; obstruction
Filibuster: an adventurer who engages in
unauthorized warfare against a country
with which his own country is at peace;
specif., any of the 19th-cent. U.S.
adventurers who led armed expeditions
into Latin American countries;
Legislature: a body of persons given the
responsibility and power to make
laws for a country or state; specif.,
the lawmaking body of a State,
corresponding to the U.S.
Congress

(B) A lace is a string that is pulled and tied to hold a shoe in place. In the same way, a drawstring is pulled and tied to hold a hood in place.
LACE: a string, ribbon, etc. used to draw together
and fasten the parts of a shoe, corset, etc. by
being drawn through eyelets or over hooks
Trouser: an outer garment, esp. for men and
boys, extending from the waist
generally to the ankles, and divided
into separate coverings for the legs;
pants ,br/> Drawstring: a string drawn through a hem, as in
the waist of a garment or mouth of
a bag, to tighten or close it by ,br/> taking up the fullness
Hood: John Bell 1831-79; Confederate general
Clasp: a metal bar attached to the ribbon of a
military decoration to show a subsequent
award of the same medal or to specify the
type or place of service
Brooch: a large ornamental pin with a clasp,
worn by women, usually at the neck
Brim: the topmost edge of a cup, glass, bowl, etc.