Statement A : Aristotle was the earliest to attempt a more scientific basis for classification, using simple morphological characters to classify plants into trees, shrubs and herbs.

Statement B : The two-Kingdom system of classification proposed by Linnaeus, which included all Plantae and Animalia, was used for a long time. 

Aristotle was the earliest to attempt a more scientific basis for classification. He used simple morphological characters to classify plants into trees, shrubs and herbs. He also divided animals into two groups, those which had red blood and those that did not. In Linnaeus' time a Two Kingdom system of classification with Plantae  and Animalia kingdoms was developed that included all plants and animals respectively.

 Classification of organisms into plants and animals was easily done and was easy to understand, but, many organisms did not fall into either category. Hence, the two kingdom classification used for a long time was found inadequate