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VII. Word Choice.

Find the most suitable word to complete the following
sentence:
All water contains:
(a) nitrogen: (b) sulphur;

(c) some dissolved solids; (d) gold.

Варіант 2.

Migration of petroleum into accumulations is thought of
largely in terms of permeability paths. It must also be thought of in
terms of fluid potential gradients-that is, deviations from
hydrostatic equilibrium in the fluids in the pore spaces of the
rocks. Permeability, as we have seen, is but one component
necessary for it to flow, and migration paths are paths of
continuously decreasing energy of each particle of the fluid
migrating decreases continuously during its migration.
Migration paths may be long or short. Hypotheses vary
from simple migration from the source rock into the adjacent
carrier bed, and through the carrier bed to the trap, on the one
hand, to multiple-stage migration from a distant source, some with
intermediate trapping from which the petroleum is spilled by
subsequent geological events, on the other. Much of the
uncertainty is because of the uncertainty about the true source
rocks and their positions.
Migration is divided into two stages: primary migration
from the source rock to the permeable carrier bed; secondary
migration from there to the trap, through one or more carrier beds.

І. Choosing the Correct Definition for a Context:

According to the last passage migration of
petroleum is divided into:

(a) one stage; (b) three stages;
(c) two stages; (d) four stages.