The Economist 2

Studying embryos beyond the current 14-day limit could lead to new treatments for illnesses such as congenital heart disease.
 
– What is the subject of this sentence?
The subject of the sentence is studying embryos beyond the current 14-day limit.
This is a gerund phrase (a phrase that uses an -ing form at the beginning of the phrase).
 
– Is the subject singular or plural?
We treat gerund phrases as singular.
 
– What is/are the tense(s) used in this sentence?
Studying embryos beyond the current 14-day limit could lead to new treatments for illnesses such as congenital heart disease.
 
Studying … could…
Subject + base form
This is a pattern for the present simple tense.
 
Could can be used:
(1) as a past tense of can
(2) in the present simple tense to indicate that something is or might be possible
 
Could in this sentence follows rule (2).
 
– Is this an active or passive sentence?
Studying embryos beyond the current 14-day limit could lead to new treatments for illnesses such as congenital heart disease.
 
The subject is the one doing the action leading.
This sentence uses active voice.
 
– Is there a noun, adjective or adverb clause in this sentence?
No, there isn’t.
 
Studying embryos beyond the current 14-day limit
= subject (gerund phrase)
 
could lead to
= verb phrase
 
new treatments
= object (noun phrase)
 
for illnesses
= prepositional phrase
 
such as congenital heart disease
= phrase
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