Presence of two types of nuclei,micronucleus and macronucleus,is characteristic of which protistan group?

Read the following statements and answer the question given below:
$(i)$ They are saprophytic protists.
$(ii)$ Under suitable conditions,they form an aggregation (called plasmodium) which may grow and spread over several feet.
$(iii)$ During unfavourable conditions,the plasmodium differentiates and forms fruiting bodies bearing spores at their tips.
Which of the following class of protists is being described by the above statements?

Heterotrophic nutrition is a characteristic of the group ..........

Which of the following characteristics is common to all protists?

"Kieselguhr" (diatomaceous earth), which is a heat-resistant substance, is obtained from which of the following?

Euglena stores food in the form of paramylum ($\beta$ 1 $\to$ 3 glucan), which is a product of the conversion of: