Read each sentence carefully and select the option with the sentence written correctly. las chicas necesitan unas sandalias blancas. las chicas necesitan una sandalias blanca. las chicas necesitan unos sandalias blancos. las chicas necesitan un sandalias blanco.

1) Las chicas necesitan unas sandalias blancas.

Explanation: This is the only sentence written correctly.

The article, noun and adjective must agree in gender & number in a sentence.

2) "una" is a singular article, but "sandalias" is a plural noun. Incorrect.

3) "unos" is a masculine article, but "sandalias" is a feminine noun. Incorrect.

4) "un" is a singular article, but "sandalias" is a plural noun. Incorrect.