Correct sentence?
a. robert told andrew that the guitar he was using should be tuned.
b. robert needed to tune his guitar and he told that to andrew.
c. robert told andrew that his guitar needed tuning.
d. robert told andrew that he needed to tune his guitar.

B. Robert needed to tune his guitar, and he told that to Andrew.

Explanation:

The other options in this question are examples of 'Intricate text'. From the options in the question,

Robert told Andrew that the guitar he was using should be tuned. : 'he' is an intricate text, and is therefore difficult for the readers to understand who it denotes to. Robert told Andrew that his guitar needed tuning. : This statement does not explain whose guitar it is. Robert told Andrew that he needed to tune his guitar. : The readers can have a confusion of who needs to tune the guitar. Robert needed to tune his guitar, and he told that to Andrew. : This sentence explains that Robert has a guitar that needs to be tuned; and he said that to Andrew about it.