TASK DEFINITION: In this task, we ask you to rewrite a sentence in simple English without changing its general meaning. Essentially, you want to make the sentence easier to read by using simpler words, utilizing more straightforward sentence structures, and omitting non-essential information etc.
PROBLEM: The retina has no sensitivity to pain , and the effects of retinal damage may not appear for hours , so there is no warning that injury is occurring .

SOLUTION: The retina does not feel pain , so damage may not be felt for hours .

PROBLEM: The undulating courses of two rivers , the Hondo and the Sarstoon River , define much of the course of the country 's northern and southern boundaries .

SOLUTION: The Hondo and the Sarstoon River make the northern and southern border .

PROBLEM: The development of Fortran paralleled the early evolution of compiler technology , and many advances in the theory and design of compilers were specifically motivated by the need to generate efficient code for Fortran programs .

SOLUTION:
Much work and research in compiler theory and design was caused by the need to generate good code for Fortran programs .