In future, each time you ask a new qn, pls start a new thread
for each new qn, and do include the topic asked in the
thread (notice that I've edited ur thread title to include the word
Equilibria). A generic "A level Chem qn" thread title isn't
informative.
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#1 - The initial pH is too low to be a weak acid, hence the acid
is a strong one.
#2 - There is only 1 vertical region, and hence only 1
equivalence point. And since the molarities and volumes of both
acid and base required to reach equivalence point are the
same, therefore both acid and base must be monoprotic.
#3 - The pH at equivalence point is approx 4, which means the
salt is acidic, which means it was generated in a Bronsted-Lowry
acid-base proton transfer reaction between a strong acid and a weak
base.
Hence the MCQ answer is Delta.