Which type of sexual reproduction is found in $Spirogyra$?

Match the Column-$I$ with Column-$II$:

Column-$I$	Column-$II$
$(a)$ Zoospores	$(i)$ Fusion between one large non-motile female gamete and a smaller motile male gamete.
$(b)$ Isogamous	$(ii)$ Flagellated (motile) asexual spores.
$(c)$ Anisogamous	$(iii)$ Gametes can be flagellated and similar in size.
$(d)$ Oogamous	$(iv)$ Fusion of two gametes dissimilar in size.

Choose the correct answer from the options given below:

The algae used in space research is

Assertion : Red algae contribute to the production of coral reefs.
Reason : Some red algae secrete and deposit calcium carbonate over their walls.

Select the correct pair from the following.

Calcium encrustation and larvicidal properties are present in