(i) Sewage : Waste matter/ feaces, urine, waste water from animals/industrial/domestic sources; that is dissolved/ suspended in water.
(ii) Effects of releasing untreated sewage into a stagnant water body;

Spread of water-borne diseases/correctly named diseases/microbes/pathogens
May be toxic/poisonous to aquatic life/organisms
Makes water unfit for consumption/use
Increased decomposition
Increased concentration of nutrients
Rapid growth of algae/aquatic plants/algal bloom/eutrophication
Depletion of oxygen
Suffocation/death of aquatic animals
Generates offensive odour/air pollution
Nutrient/nitrate/phosphate enrichment/accumulation in a water body; as a result of breakdown by bacteria.

(b) Surface terracing as a soil conservation method :
A method of controlling erosion on a gentle/steep slope of hill; flat horizontal areas are constructed on which crops are cultivated; following the contour; steps/walls are built along the contous; plughing is also done along the contours; reduces the speed of water running down the slopes.
(c) Adaptation : Is the possession of the characteristic/trait/behaviour/structure/feature; that evolved over a period of time; enable an organism to survive and reproduce; in response to changes in the environment/habitat.
(d) Adaptation of; (i) Hydrophytes

Some hydrophytes lack/have reduced roots/root hairs/root caps
do not need firm anchorage in water/wetland
presence of large air space parenchyma in roots/leaves; provide support for buoyancy
Presence of hairs on the leaves; to prevent blockage of the stomata
stomatal pores; occur only at the upper epidermis of the leaves to aid transpiration/loss of water
numerous adventitious roots and root hairs; aid the absorption of water/mineral salts
small size of the plant; for buoyancy/floating in water
waxy upper surface of the leaf; to prevent clogging of the leaf by water
long petiole/leaf stalk to support/ expose the broad lamina for photosynthesis
long flower stalk/pedicel; to expose flower for pollination/ pollinating agents
presence of breathing roots/pneumatophores; for breathing/gaseous exchange.

Xerophytes

possession of thick succulent leaves/stem; for storing water
reduction of leaves to spines; to reduce water loss/rate of transpiration
thick waxy cuticle on epidermis; to reduce water-loss/transpiration
possession of long tap root system; tp obtain water from great depth of soil
presence of sunken stomata; to reduce water loss
reduced number of stomata; to prevent excessive water loss
possession of multiple epidermal layers; for water conservation/to reduce water loss.