Explanation:
Methyl carbanion is a negatively charged species with the formula CH3-. The shape of a molecule or ion is determined by the arrangement of its atoms in space. The shape of methyl carbanion can be determined by considering its electronic and molecular geometry.

Electronic geometry:
The electronic geometry of methyl carbanion is tetrahedral. This is because the carbon atom has four electron groups around it (three bonding pairs and one lone pair), which leads to a tetrahedral electronic geometry.

Molecular geometry:
The molecular geometry of methyl carbanion is trigonal pyramidal. This is because the carbon atom is sp3 hybridized and has four electron groups around it. The three bonding pairs are arranged in a trigonal planar shape, while the lone pair is located in the fourth position. The repulsion between the lone pair and the bonding pairs causes the molecule to adopt a trigonal pyramidal shape.

Comparison with other molecules:
Based on the molecular geometry, the shape of methyl carbanion is similar to that of NH3 (ammonia). NH3 also has a trigonal pyramidal shape because the nitrogen atom is sp3 hybridized and has one lone pair and three bonding pairs. However, the shape of methyl carbanion is different from that of BF3 (trigonal planar) and methyl carbocation (trigonal planar with a vacant p orbital).

Methyl carbanion is sp₃ hybridized, with three bond pairs and one lone pair, same is the case with NH₃.