Please select the eligibility criteria that correspond to the clinical trial below.
Title: The Nurses' Health Study (NHS) and Health Professionals Follow-Up Study (HPFS) Folic Acid Prevention Trial
Brief Summary: RATIONALE: Chemoprevention is the use of certain substances to keep cancer from forming. The use of folic acid may prevent colorectal cancer.

PURPOSE: This randomized clinical trial is studying how well folic acid works compared with a placebo in preventing colorectal polyps in patients who have had previous colorectal polyps.


Options:
A: Inclusion Criteria:

* 18-35 years old
* Currently married
* Currently living in one of the 10 communes and intends to live in the areas for 24 months following recruitment
* Plans to have children in the next year
* Agrees to participate with informed consent

Exclusion Criteria:

* Currently pregnant
* Delivered in the previous six months
* Regularly consumed IFA or MM supplements in the past 2 months
* Severe anemia (Hb \< 7 g/L)
* History of high risk pregnancy including abruptio placenta, placenta previa, gestational diabetes, pregnancy induced hypertension, coagulation disorders, thrombocytopenia or chronic vascular, renal or systemic disease and drug use
* Chronic hematological diseases, hereditary defects of red cells or hemoglobin
B: Inclusion Criteria:

* Married women of reproductive age identified as a new pregnancy using a urine test

Exclusion Criteria:

* Menopausal or sterilized woman or currently already pregnant or breastfeeding an infant \<9 months of age
C: Inclusion Criteria:

* Women with cleft lip with/out palate (CLP), 16 to 45 years of age registered at the study clinics in Brazil or Women (16 to 45 years of age) with at least one natural child of any age with CLP registered at the study clinics.
* Women must reside in the catchment area of the study, which includes the states where the study clinics are located and surrounding states.

Exclusion Criteria:

* Consanguineous couples (up to third degree, i.e. first cousins or closer).
* Pregnany at the time of recruitment. Women will be recontacted later at an appropriate time for participation in the study.
* Couples either one of which have been sterilized.
* Taking any form of seizure medication.
* Planning to move outside of the study catchment area within the next year.
* B12 deficiency (\<174 pg/mL or 129.15 pmol/L).
* Being allergic to folic acid.
D: DISEASE CHARACTERISTICS:

Inclusion criteria:

* Participated in the Nurses' Health Study (NHS I) or the Health Professionals Follow-Up Study (HPFS) and have had a previous confirmed diagnosis of adenomatous polyp of the colon or rectum
* Plan on having an endoscopy within 4 years after initiation of the trial
* Must release medical records regarding past and any future endoscopies

PATIENT CHARACTERISTICS:

Inclusion criteria:

* Plasma vitamin B12 concentration of ≥ 300 pg/mL or have a vitamin B12 concentration between 200 and 299 pg/mL and a methylmalonic acid (MMA) level ≤ 32 µg/L

Exclusion criteria:

* Diagnosis of cancer other than non-melanoma skin cancer, or early stage breast or prostate cancer
* Diagnosis of homocystinemia
* Diagnosis of pernicious anemia
* Any gastrointestinal disorder that could lead to a vitamin B12 deficiency
* Diagnosis of cirrhosis or pancreatitis
* Diagnosis of epilepsy, Alzheimer's disease, Parkinsonism, and psychiatric disorders that may interfere with normal functioning

PRIOR CONCURRENT THERAPY:

Exclusion criteria:

* No prior gastrectomy, total colectomy, or pancreatectomy
* Other concurrent multivitamins or supplements that contain folic acid (they may take specific supplements, such as A, C, E, calcium, and iron, or antioxidant formula vitamins)
* No concurrent methotrexate or anticonvulsant

Answer: D