法律规定父母有义务抚养未成年子女。

The law ___obligates parents to support their minor children.

根据合同条款，公司有义务在30天内完成项目交付。

The company is ___obligated to complete the project delivery within 30 days under the contract terms.

这些微生物是专性寄生物，只能在宿主细胞内繁殖。

These microbes are ___obligate parasites that can only reproduce inside host cells.