Question

add subordinate clause to expand the sentence 1.we saw an aeroplane

Answer 1

we saw an aeroplane flying in the sky

Answer 2

Subordinate clauses remain under the influence of the uniclausal sentence or the main Clause . These clauses connect to the main clause using a subordinating or the relative conjunction. These clauses can be of three types namely the noun clause, the adjective clause and the adverb clause. Another category of clauses are coordinate clauses which relate to the main clause using a coordinating conjunction.

The probable answer required in accordance with these rules mentioned above will be :

We saw an aeroplane which was white. (adjective clause).