Anatomy of Flowering Plants

Primary tissues are formed by the activity of the apical meristems; secondary tissues are formed by the lateral meristems (vascular cambium and cork cambium).
In a woody dicot tree, the stem and the root undergo extensive secondary growth, so they consist mainly of secondary tissues (wood and bark).
Leaves, flowers and fruits are lateral appendages of limited growth; they do not have a cambium that forms secondary tissues, so they consist mainly of primary tissues throughout their life.
The shoot tips and root tips are also primary, but they are only small regions of the stem and root.
So, as given in the answer key, the parts that mainly consist of primary tissues are the flowers, fruits and leaves.

Paper is made from cellulose fibres.
In wood, the cellulose fibres are bound together by lignin, a complex polymer that makes the cell walls hard and gives a brown colour.
In pulp manufacture, the wood chips are treated with chemicals (for example in the sulphate or sulphite process) that dissolve the lignin.
This frees the cellulose fibres and gives a relatively pure cellulose pulp, which is then bleached and made into paper.
Breaking down the cellulose itself would destroy the fibres needed for paper, and removing water or oils is not the key step.
So the important step is the preparation of pure cellulose by removing lignin.