Answer:
was instead of were
were instead of was
is instead of are
offer instead of offers
Explanation:
1-As a teenager, Sir Paul Smith, now one of Britain’s best-known fashion designers, was on track for a very different career.
In sentence 1, the subject is Sir Paul Smith which is singular therefore was on track is the proper subject-verb agreement.
2-A serious car accident at age 17 put him in hospital for six months and his dreams were all but over...
In sentence 2, the subject of the second part is dreams which is plural therefore, were is the correct form of the past tense of be.
3-His 531 collection of cyclejackets, jerseys and shorts is understated, ...
In this sentences 3, the head of the phrase is collection which is singular therefore is agrees with collection.
4-...using materials such as Ventile cotton and Merino wool, which offer breathability and durability.
In sentence 4, the subject is materials which is plural therefore, offer is the correct form of the simple present.
