B.

integument with muscles

Loose or aerolar connective tissue is the most generalized connective tissue, which is spread extensively throughout the body - under the skin and epithelia, around and in between the muscles, around nerves and blood vessels between lobes and lobules of compound glands, in the submucosa of respiratory and gastrointestinal tracts.
It functions mainly for binding the parts together but also helps in sliding movement of epithelia, muscles and other parts and also forms the internal histological framework or stroma of many solid organs.

C.

Tubular parts of nephrons - Cuboidal epithelium

Areolar tissue is a to the body loose connective tissue, and provide flexibility and cushioning Adipose tissue is also loose connective tissue while, the tendon is a dense connective tissue, which connect the muscleswith the bone, carilage is composed of specified connective tissue cvalled chondrocytes that produce a large amount of extracellular matrix composed of collagen fibre.

D.

nucleated and without haemoglobin

RBCs or erythrocytes of frog are oval, disc-like biconvex, have centrally placed nucleus and with haemoglobin. Usually in mammals (including human), RBCs are circular and non-nucleated except those of family Camilladae (camels, llamas, etc), which have nucleated RBCs

A.

Frogs respire on land and in the water by two different methods. In water, skin acts as an aquatic respiratory organ (cutaneous respiration). Dissolved O₂ in the water is exchanged through the skin by diffusion. On land, the buccal cavity skin and lungs act as the respiratory organs. The respiration by lungs is called is called pulmonary respiration.
In frog, heart has three -chambers, two atria and one ventricle, and is covered by a membrane called pericardium
The frog excreates area and thus is a ureotelic animal. It never becomes uricotelic. In the frog, fertilisation is external and takes place in water.

D.

ammonotelic when plenty of water is available

Class Oligochaeta includes terrestrial earthworms and some other species that live in fresh water. Aquatic oligochaetes excrete ammonia while terrestrial oligochaetes excrete urea but Lumbricus produces both ammonia and urea.