Final answer:
The best version of the underlined portions of sentences 4 and 5 is Option E: 'died in 1757, when Martha was only 26 years old.', as it provides a concise and clear temporal link between the events.
Step-by-step explanation:
The question involves choosing the correct version of the underlined sentences to accurately convey the relationship between Custis's death and Martha's age at that time. Considering the options:
- Option A ('died in 1757, because Martha was only 26 years old.') incorrectly implies causation.
- Option B ('died in 1757. Martha was only 26 years old.') simply states two facts without connecting them.
- Option C ('died in 1757, and that was when Martha was only 26 years old.') is wordy and awkward in construction.
- Option D ('died in 1757, the year when Martha was only 26 years old.') correctly connects the events but is also unnecessarily wordy.
- Option E ('died in 1757, when Martha was only 26 years old.') concisely indicates that Martha's age at the time of Custis's death was 26, making it the best choice.
Therefore, the best version of the underlined portion is Option E: 'died in 1757, when Martha was only 26 years old.', as it concisely and clearly provides the temporal link between the two pieces of information.