**Core Concept**
The maturation of fetal lungs is a critical aspect of fetal development, especially after 28 weeks of gestation. The presence of surfactants, such as lecithin and sphingomyelin, and the maturation of type II pneumocytes are essential for the proper functioning of the fetal lungs.

**Why the Correct Answer is Right**
After 28 weeks of gestation, the fetal lungs are considered viable, meaning they are capable of independent gas exchange if born prematurely. This viability is often associated with a birth weight of greater than 1000 grams. Additionally, the lecithin/sphingomyelin (L/S) ratio increases significantly after 28 weeks, typically exceeding 2 by this gestational age. Furthermore, type II pneumocytes, which produce surfactants, become more mature and functional, and phosphatidylglycerol, a specific type of surfactant, is produced and accumulates in the alveoli. The presence of phosphatidylglycerol is a reliable indicator of fetal lung maturity.

**Why Each Wrong Option is Incorrect**
**Option B:** The statement that the birth weight must be greater than 1000 grams is not universally applicable, as some premature infants may be viable and survive with birth weights less than 1000 grams.
**Option C:** Option C is incorrect because the presence of type II pneumocytes is not a specific indicator of fetal lung maturity; rather, it is the maturation of these cells that is crucial.
**Option D:** While phosphatidylglycerol is an indicator of fetal lung maturity, it is not the only factor; the presence of lecithin and the L/S ratio also play critical roles.

**Clinical Pearl / High-Yield Fact**
The L/S ratio is a reliable indicator of fetal lung maturity, with a ratio of 2 or greater typically indicating mature lungs. However, it is essential to note that a single abnormal test result does not necessarily indicate immaturity, as other factors may influence the result.

**✓ Correct Answer: A. abd. Both the fetal lungs are viable, the birth weight is greater than 1000 grams, and both lecithin/sphingomyelin ratio >2 and phosphatidylglycerol present.**