**Core Concept**
Pulmonary tuberculosis (TB) in pregnancy poses a significant challenge due to the need to balance the treatment of the mother's TB with the potential risks to the fetus. The first trimester is a critical period of fetal development, and any teratogenic effects of antitubercular therapy (ATT) must be carefully considered.

**Why the Correct Answer is Right**
The treatment of choice for sputum-positive pulmonary TB in the 1st trimester of pregnancy involves the use of a combination of first-line antitubercular drugs, including isoniazid (INH), rifampicin (RMP), pyrazinamide (PZA), and ethambutol (EMB). This regimen is recommended by the World Health Organization (WHO) and is considered safe for use during pregnancy. The key is to use the standard four-drug regimen, which has been extensively studied and shown to be effective in treating TB in pregnant women.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because monotherapy with a single drug like INH is not sufficient to treat pulmonary TB, as it can lead to the development of drug-resistant TB.
* **Option B:** This option is incorrect because the use of streptomycin (SM) is contraindicated in pregnancy due to its potential to cause ototoxicity and nephrotoxicity in the fetus.
* **Option C:** This option is incorrect because the use of second-line antitubercular drugs like fluoroquinolones and aminoglycosides is generally reserved for patients with severe or drug-resistant TB, and their use in pregnancy is not well-studied.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the standard four-drug regimen for treating pulmonary TB in pregnancy should be continued for at least 6 months, even if the patient becomes culture-negative earlier. This is to ensure that the infection is fully cleared and to prevent the development of drug-resistant TB.

**Correct Answer:** C.