(i)
I – Crown / Enamel
II – Dentine
III – Cement / Periodontal membrane
IV – Jaw bone / Root
V – Pulp Cavity

(ii)
I – Protects teeth from harmful bacteria
– Enable teeth withstand pressure of chewing
– Cutting / chewing / protects dentine / protect pulp cavity
III – hold tooth firmly (in socket / Jaw bone)

(iii) V – Pulp cavity

(iv)  avoid using sharp-pointed objects
 avoid having dry mouth
 use water containing fluorides to wash teeth / mouth
 avoid smoking
 the teeth should be cleaned regularly after each meal / remove food particle from the teeth / flossing
 wash the mouth vigorously after each meal
 regular visit to the dentist
 avoid eating too hot foods
 avoid eating too much sugary food
 avoid eating too cold food / taking too cold drinks

(b)(i)

(i) Refraction of light

(ii) I – Normal
II – Incident ray
III – angle of incidence / incident angle
IV – angle of refraction
V – refracted ray

(iii) Rays from the object at the bottom are bent away from the normal as they come out of the water. In a straight line, these rays appear to come from a point above the bottom

(c)

(i) I – Retort / clamp stand
II – filter paper
III – funnel

(ii)
 to prevent the residue / solid / insoluble particles / mud from entering the filtrate
 to filter (solid / insoluble particles / residue)
 to separate the nud, solid / insoluble particles from the water

(iii) Water

(iv)  it has a density of 1 gcm –3 / 1000 kgm–3
 it boils at 100°C
 it freezes at 0°C (at 1 atm)
 it is colourless
 it is tasteless / insipid
 it is odourless
 it has a high surface tension, etc

(v)
 foam
 cotton wool
 glass wool
 Clean / white cloth

(d)

(i) Erosion

(ii)
 Deforestation
 bush burning
 continuous cropping
 cultivation / ploughing along slope
 crop removal
 excessive use of chemical / inorganic fertilizers
 overgrazing

(iii)
 planting cover crops
 terracing
 cultivating / ploughing across slope / contour
 heavy mulching
 constructing drainage channels
 planting trees beside farm
 strip cropping
 contour binding

(iv)
 soil organisms
 nutrients (macro / micro) / mineral matter
 soil particles / mineral matter
 growing crops
 air
 organic matter / humus