When 2-phenylacetaldehyde is added dropwise to benzaldehyde in the presence of sodium hydroxide they undergo a crossed aldol reaction to form 3-hydroxy-2,3-diphenylpropanal?

Carbonyl Compounds containing alpha proton readily donates alpha acidic proton when treated with strong Base. In given statement 2-phenylacetaldehyde is converted into Enolate and Enolates acts as a nucleophile and attacks carbonyl group of Benzaldehyde. The mechanism of given reaction is as follow, the movement of electrons is shown by RED arrows,

Weathering is the process of breaking large rocks and boulders into much smaller ones. Weathering can be brought about by wind and water mostly. Sometimes even biological forces account for some types of weathering.