There is the gene that causes hemophilia which, if paired with a healthy gene, the individual will not develop the disease’s symptoms.
Meaning. Gene --> Haemophilia. However, when gene (paired with healthy gene) ---> individual won't develop the symptoms.
(A) There is the gene that causes hemophilia which, if paired with a healthy gene, the individual will not develop
incorrect modifier usage
(B) The gene that causes hemophilia which, if paired with a healthy gene, then the individual will not develop
incorrect modifier usage; also, the use of conditional 'than' is incorrect
(C) There is the gene that causes hemophilia, and if paired with a healthy gene, the individual will not develop
doubtful over the subject of 'if paired with a healthy gene'..S-V agreement error
(D) If paired with a healthy gene, the gene that causes hemophilia will not result in the individual’s developing
Correct modifier reference..also, correct meaning as described above
(E) Hemophilia is caused by a gene that, if paired with a healthy gene, will not develop in the individual
It's not the gene that develops the symptoms, rather it's a the typical condition that leads to the individual's developing
symptoms
(D) is the CORRECT answer