In the following sentence, the bracketed part needs attention. Choose the option that best improves or corrects the sentence if necessary. 'There are two pens here and (either write) well.'

Introduction / Context:
This sentence improvement question focuses on subject verb agreement and the correct use of 'either' with singular verbs. The sentence 'There are two pens here and (either write) well.' contains a bracketed verb phrase that must be checked for agreement with its subject. Competitive exams frequently test small but important points like this in grammar sections.

Given Data / Assumptions:
- Original sentence: 'There are two pens here and either write well.'
- Options: 'either have written', 'either wrote well', 'either writes', 'No improvement'.
- 'Either' refers to one or the other of the two pens, considered individually.

Concept / Approach:
When 'either' is used as a pronoun meaning 'one or the other of two', it is grammatically singular and therefore takes a singular verb. For example, we say 'Either is fine' or 'Either works for me'. In the sentence, 'either write well' incorrectly uses the plural form 'write' with a singular subject. The correct form is 'either writes well'. The other options either change the tense unnecessarily or are not appropriate for this simple present, general statement about the pens.

Step-by-Step Solution:
Step 1: Identify the grammatical subject after the conjunction 'and': it is 'either' (of the two pens). Step 2: Recognise that 'either' in this usage is singular and should take a singular verb. Step 3: The singular present form of 'write' for third person singular is 'writes'. Step 4: Therefore, the corrected clause should read 'either writes well'. Step 5: Compare this with the options and select 'either writes' as the correct improvement.

Verification / Alternative check:
Read the fully corrected sentence: 'There are two pens here and either writes well.' This means that out of the two pens, any one you pick will write well. The tense is simple present, suitable for expressing a general fact. 'Either have written' is present perfect and grammatically wrong because 'either' does not take 'have' in this way. 'Either wrote well' changes the tense to simple past, which is not required, and still sounds awkward. 'No improvement' is incorrect because 'either write' breaks subject verb agreement by using a plural verb with a singular subject.

Why Other Options Are Wrong:
'Either have written' is wrong because 'either' requires 'has' in the present perfect, not 'have', and even then the aspect is unnecessary for this statement. 'Either wrote well' is wrong because it switches the sentence into the past tense and remains stylistically weak compared with the standard general present. 'No improvement' is wrong because it would keep the grammatically incorrect 'either write' form.

Common Pitfalls:
Students sometimes forget that 'either' and 'neither' used before verbs are singular. They may be misled by the plural noun 'two pens' earlier in the sentence and incorrectly choose a plural verb. To avoid this, always focus on the immediate subject of the verb. After 'either' and 'neither' in such structures, remember to use singular verb forms: 'either is', 'either does', 'either writes' and similarly 'neither is', 'neither does', 'neither writes'.

Final Answer:
The correct improvement is 'either writes', giving 'There are two pens here and either writes well.'