MSMA (monosodium methanearsonate) is an arsenic-based grass killer. It kills grassy weeds such as crabgrass and goosegrass without harming most turfgrasses. It contains organic arsenic that, according to the University of Tennessee Extension, is less harmful than aspirin.
There are several styles of hearing aids available, from the smallest - Invisible in the Canal (IIC) to the largest and strongest - Power Behind the Ear (BTE), and the very popular Receiver in the Canal (RIC) - made to fit most hearing losses while remaining nearly unseen.
Four Types of Teaching Aids. There are four main types of Teaching Aids 1. Auditory Aids These teaching aids act through ear for which peaceful and calm atmosphere is necessary. Ability to listen attentively should be foster among the students. (i) The Gramophone This teaching aid is used for different purposes. It is useful for the teaching of music and language.