It was also so clearly written that it could ... by ordinary people

Question 7

The sentence requires a verb form that agrees with 'it' and fits the context of being understood.

1. 'to be read and understood' - This option correctly uses the infinitive form after 'could'.
2. 'read and understood' - This option is grammatically incorrect as it omits the auxiliary 'be' or other modal verbs.
3. 'be read and understand' - This option is grammatically incorrect because 'understand' should be in the past participle form to parallel 'read'.
4. 'be read and understood' - This option correctly uses the passive infinitive form after 'could'.

Considering the options, 'to be read and understood' and 'be read and understood' are grammatically plausible. However, 'could' is a modal verb and is typically followed by the base form of the verb or the passive infinitive. 'be read and understood' fits this structure perfectly, implying that the writing was clear enough for ordinary people to read and understand it.

Answer: d. be read and understood