Which organ develops and is fully functional in the first trimester?
heart
brain
liver
lungs

The organ that becomes fully functional during the first trimester is the heart

Option A

Explanation:

The gametes which are formed by meiosis fuse with each other to form the zygote , the homozygous gametes join together to form the heterozygous zygote. This zygote which is a single cell undergoes mitotic division to form the blastula.

The cells at this stage are non-differentiated; these cells later differentiate into different organs and develop a full grown organism. The development of organs in a human body is sequential and thus among the above the heart develops in the first trimester.

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