Question

this is a piece of tillite. it formed from a type of sediment called till. till is made up of grains of various sizes, from mud to boulders. the grains are often uneven in shape. till is deposited by glaciers as they melt. many layers of till can build up at the mouth of a glacier. tillite forms when these layers are pressed together to form rock. what type of rock is tillite? sedimentary metamorphic igneous

Explanation:

沉积岩是由沉积物经过压实和胶结等作用形成的岩石。冰碛岩由冰川融化沉积的冰碛物（各种大小的颗粒）层层堆积后压实形成，符合沉积岩的形成特征。变质岩是原岩在高温高压等条件下发生变质作用形成；火成岩是岩浆冷却凝固形成。

Answer:

A. sedimentary