The verbal group: tenses

Past, Present Perfect
has been suggested

has been accepted












provided
showed


extracted



may have caused

have reopened
Present



break down
do

denature,
attack

are fed
appear
is thought
may autoxidise
(may)
polymerise
Future

Materials and Methods
Aortas were obtained at autopsy, within 6-­‐12 hours
of death, at the University Hospital, Barchester.
Aortas were classified as being at stage 0, I, II or III
of atherosclerosis according to the appearance of
the intima (6), and the adventitia was rapidly
removed.


were obtained

were classified


was removed








Discussion
If the peroxides measured in lipid extracts from the
arterial wall are artifacts, how can we explain Lufton
and Sowerby's findings (1) that the peroxide content
is correlated with degree of atherosclerosis? It has
recently been discovered (6) that arterial lipids
become progressively more unsaturated with
increasing degree of atherosclerosis. Among the
lipid classes, cholestryl esters show the most striking
increase in unsaturation, and the proportion of
cholesteryl esters show the most striking increase in
unsaturation, and the proportion of cholesteryl
esters relative to the other lipids also rises (9, 10).
The more atherosclerotic the aorta, therefore, the
more susceptible will its lipids be to explain the
observed correlation.





has been discovered



are
can explain




show

show

rises
















will be

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Basic English Grammar Module: Unit 2B. Independent Learning Resources
© Learning Centre University of Sydney. This Unit may be copied for individual student use.
14
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You can now check the answers in the Answer Key at the back of the unit.
2.0 Meanings of the tenses
In the next section we will do two things. First, we will look at the meanings of these
tenses and then we will go on to look at when the writers of academic texts use these
tenses.
As a writer you take your position in present time. You then have to decide from your
position in the present whether the things you are writing about are happening now
(present), whether they have already happened (past) or whether they will happen in
the future.