This question was popular among the candidates.  In 5(a-b), most of the candidates could neither define the term nursery as used in crop production, nor give the reasons for establishing a nursery in crop production.  Also, most of them could not mention the characteristics of weeds that make them difficult to control as required in 5(c).  However in 5(d-f), majority of the candidates were able list the methods of controlling weeds, state the ways by which diseases are spread among crops and mention the effects of diseases on crops.
The expected answers include:
(a)      Definition of nursery in crop production
           Nursery is a place where young plants are raised under intensive
            management practices for later transplanting into permanent fields/plot
(b)     Reasons for establishing a nursery in crop production
            -     Promotes economy of seeds/efficient utilization of seeds
            -     Seedlings receive more intensive care e.g. watering, manuring and protection  
                  from animals, diseases and pests
           -Creates an opportunity for selecting healthy, vigorous and disease-free seedlings for transplanting
          - Seeds that are difficult to germinate in the field are better raised in the nursery e.g carrot, cabbage

  Characteristics of weeds that make them difficult to control
             -     Ability to produce many seeds
             -     Weed seeds have long period of dormancy
             -     Some weeds have deep root systems used for absorbing water from deeper
                   horizons in dry soils
             -     Some weeds have modified root system for storing food which they thrive on for
                   long periods e.g. waterleaf
             -     A good number of weeds have very efficient means of dispersal
             -     Weeds survive under marginal/poor soil by virtue of profuse rooting systems
                   and their minimum nutrient requirement status
             -     Some weeds have very fast growth rates
             -     Weeds survive under adverse environmental conditions by means of
                   structures such as stolon, rhizomes